diff --git a/api_docs/changelog.md b/api_docs/changelog.md
index 6922244052..c2eb725d76 100644
--- a/api_docs/changelog.md
+++ b/api_docs/changelog.md
@@ -20,6 +20,16 @@ format used by the Zulip server that they are interacting with.
 
 ## Changes in Zulip 8.0
 
+**Feature level 229**
+
+* [`PATCH /messages/{message_id}`](/api/update-message), [`POST
+  /messages`](/api/send-message): Topic wildcard mentions involving
+  large numbers of participants are now restricted by
+  `wildcard_mention_policy`. The server now uses the
+  `STREAM_WILDCARD_MENTION_NOT_ALLOWED` and
+  `TOPIC_WILDCARD_MENTION_NOT_ALLOWED` error codes when a message is
+  rejected because of `wildcard_mention_policy`.
+
 **Feature level 228**
 
 * [`GET /events`](/api/get-events): `realm_user` events with `op: "update"`
diff --git a/version.py b/version.py
index a4e1f6c726..7f77715976 100644
--- a/version.py
+++ b/version.py
@@ -33,7 +33,7 @@ DESKTOP_WARNING_VERSION = "5.9.3"
 # Changes should be accompanied by documentation explaining what the
 # new level means in api_docs/changelog.md, as well as "**Changes**"
 # entries in the endpoint's documentation in `zulip.yaml`.
-API_FEATURE_LEVEL = 228
+API_FEATURE_LEVEL = 229
 
 # Bump the minor PROVISION_VERSION to indicate that folks should provision
 # only when going from an old version of the code to a newer version. Bump
diff --git a/web/src/compose.js b/web/src/compose.js
index 263df67f8d..574c613f0e 100644
--- a/web/src/compose.js
+++ b/web/src/compose.js
@@ -5,6 +5,7 @@ import $ from "jquery";
 import _ from "lodash";
 
 import render_success_message_scheduled_banner from "../templates/compose_banner/success_message_scheduled_banner.hbs";
+import render_wildcard_mention_not_allowed_error from "../templates/compose_banner/wildcard_mention_not_allowed_error.hbs";
 
 import * as channel from "./channel";
 import * as compose_banner from "./compose_banner";
@@ -180,16 +181,26 @@ export function send_message(request = create_message_object()) {
         send_message_success(request, data);
     }
 
-    function error(response) {
-        // If we're not local echo'ing messages, or if this message was not
-        // locally echoed, show error in compose box
+    function error(response, server_error_code) {
+        // Error callback for failed message send attempts.
         if (!locally_echoed) {
-            compose_banner.show_error_message(
-                response,
-                compose_banner.CLASSNAMES.generic_compose_error,
-                $("#compose_banners"),
-                $("textarea#compose-textarea"),
-            );
+            if (server_error_code === "TOPIC_WILDCARD_MENTION_NOT_ALLOWED") {
+                // The topic wildcard mention permission code path has
+                // a special error.
+                const new_row = render_wildcard_mention_not_allowed_error({
+                    banner_type: compose_banner.ERROR,
+                    classname: compose_banner.CLASSNAMES.wildcards_not_allowed,
+                });
+                compose_banner.append_compose_banner_to_banner_list(new_row, $("#compose_banners"));
+            } else {
+                compose_banner.show_error_message(
+                    response,
+                    compose_banner.CLASSNAMES.generic_compose_error,
+                    $("#compose_banners"),
+                    $("textarea#compose-textarea"),
+                );
+            }
+
             // For messages that were not locally echoed, we're
             // responsible for hiding the compose spinner to restore
             // the compose box so one can send a next message.
diff --git a/web/src/echo.js b/web/src/echo.js
index bd337cf288..cb062dc85f 100644
--- a/web/src/echo.js
+++ b/web/src/echo.js
@@ -96,7 +96,7 @@ function resend_message(message, $row, {on_send_message_success, send_message})
         failed_message_success(message_id);
     }
 
-    function on_error(response) {
+    function on_error(response, _server_error_code) {
         message_send_error(message.id, response);
         setTimeout(() => {
             hide_retry_spinner($row);
diff --git a/web/src/markdown.js b/web/src/markdown.js
index c89e5de21a..b2c804fbb6 100644
--- a/web/src/markdown.js
+++ b/web/src/markdown.js
@@ -85,13 +85,22 @@ function contains_problematic_linkifier({content, get_linkifier_map}) {
     return false;
 }
 
+function contains_topic_wildcard_mention(content) {
+    // If the content has topic wildcard mention (@**topic**) then don't
+    // render it locally. We have only server-side restriction check for
+    // @topic mention. This helps to show the error message (no permission)
+    // via the compose banner and not to local-echo then fail due to restriction.
+    return content.includes("@**topic**");
+}
+
 function content_contains_backend_only_syntax({content, get_linkifier_map}) {
     // Try to guess whether or not a message contains syntax that only the
     // backend Markdown processor can correctly handle.
     // If it doesn't, we can immediately render it client-side for local echo.
     return (
         contains_preview_link(content) ||
-        contains_problematic_linkifier({content, get_linkifier_map})
+        contains_problematic_linkifier({content, get_linkifier_map}) ||
+        contains_topic_wildcard_mention(content)
     );
 }
 
diff --git a/web/src/message_edit.js b/web/src/message_edit.js
index 7426d20dcf..8af05d5988 100644
--- a/web/src/message_edit.js
+++ b/web/src/message_edit.js
@@ -2,6 +2,7 @@ import ClipboardJS from "clipboard";
 import $ from "jquery";
 
 import * as resolved_topic from "../shared/src/resolved_topic";
+import render_wildcard_mention_not_allowed_error from "../templates/compose_banner/wildcard_mention_not_allowed_error.hbs";
 import render_delete_message_modal from "../templates/confirm_dialog/confirm_delete_message.hbs";
 import render_confirm_moving_messages_modal from "../templates/confirm_dialog/confirm_moving_messages.hbs";
 import render_message_edit_form from "../templates/message_edit_form.hbs";
@@ -1070,13 +1071,23 @@ export function save_message_row_edit($row) {
 
                 hide_message_edit_spinner($row);
                 if (xhr.readyState !== 0) {
+                    const $container = compose_banner.get_compose_banner_container(
+                        $row.find("textarea"),
+                    );
+
+                    if (xhr.responseJSON?.code === "TOPIC_WILDCARD_MENTION_NOT_ALLOWED") {
+                        const new_row = render_wildcard_mention_not_allowed_error({
+                            banner_type: compose_banner.ERROR,
+                            classname: compose_banner.CLASSNAMES.wildcards_not_allowed,
+                        });
+                        compose_banner.append_compose_banner_to_banner_list(new_row, $container);
+                        return;
+                    }
+
                     const message = channel.xhr_error_message(
                         $t({defaultMessage: "Error editing message"}),
                         xhr,
                     );
-                    const $container = compose_banner.get_compose_banner_container(
-                        $row.find("textarea"),
-                    );
                     compose_banner.show_error_message(
                         message,
                         compose_banner.CLASSNAMES.generic_compose_error,
diff --git a/web/src/transmit.js b/web/src/transmit.js
index 48efd18d07..29180cb4df 100644
--- a/web/src/transmit.js
+++ b/web/src/transmit.js
@@ -71,7 +71,7 @@ export function send_message(request, on_success, error) {
                 }
 
                 const response = channel.xhr_error_message("Error sending message", xhr);
-                error(response);
+                error(response, xhr.responseJSON?.code);
             },
         });
     } finally {
@@ -97,7 +97,7 @@ export function reply_message(opts) {
         //       already handles things like reporting times to the server.)
     }
 
-    function error() {
+    function error(_response, _server_error_code) {
         // TODO: In our current use case, which is widgets, to meaningfully
         //       handle errors, we would want the widget to provide some
         //       kind of callback to us so it can do some appropriate UI.
diff --git a/web/templates/compose_banner/wildcard_mention_not_allowed_error.hbs b/web/templates/compose_banner/wildcard_mention_not_allowed_error.hbs
index 3b1d861cd3..b05ba39e23 100644
--- a/web/templates/compose_banner/wildcard_mention_not_allowed_error.hbs
+++ b/web/templates/compose_banner/wildcard_mention_not_allowed_error.hbs
@@ -1,5 +1,9 @@
 {{#> compose_banner }}
     <p class="banner_message">
-        {{#tr}}You do not have permission to use <b>@{stream_wildcard_mention}</b> mentions in this stream.{{/tr}}
+        {{#if stream_wildcard_mention}}
+            {{#tr}}You do not have permission to use <b>@{stream_wildcard_mention}</b> mentions in this stream.{{/tr}}
+        {{else}}
+            {{#tr}}You do not have permission to use <b>@topic</b> mentions in this topic.{{/tr}}
+        {{/if}}
     </p>
 {{/compose_banner}}
diff --git a/web/templates/settings/organization_permissions_admin.hbs b/web/templates/settings/organization_permissions_admin.hbs
index 12cf4b3582..dae4518a10 100644
--- a/web/templates/settings/organization_permissions_admin.hbs
+++ b/web/templates/settings/organization_permissions_admin.hbs
@@ -101,7 +101,7 @@
                     </select>
                 </div>
                 <div class="input-group">
-                    <label for="realm_wildcard_mention_policy" class="dropdown-title">{{t "Who can use @all/@everyone mentions in large streams" }}
+                    <label for="realm_wildcard_mention_policy" class="dropdown-title">{{t "Who can notify a large number of users with a wildcard mention" }}
                         {{> ../help_link_widget link="/help/restrict-wildcard-mentions" }}
                     </label>
                     <select name="realm_wildcard_mention_policy" id="id_realm_wildcard_mention_policy" class="prop-element settings_select bootstrap-focus-style" data-setting-widget-type="number">
diff --git a/web/tests/transmit.test.js b/web/tests/transmit.test.js
index 9c951fe38d..01fd6aa798 100644
--- a/web/tests/transmit.test.js
+++ b/web/tests/transmit.test.js
@@ -100,6 +100,34 @@ run_test("transmit_message_ajax_reload_pending", () => {
     assert.ok(reload_initiated);
 });
 
+run_test("topic wildcard mention not allowed", ({override}) => {
+    /* istanbul ignore next */
+    const success = () => {
+        throw new Error("unexpected success");
+    };
+
+    /* istanbul ignore next */
+    const error = (_response, server_error_code) => {
+        assert.equal(server_error_code, "TOPIC_WILDCARD_MENTION_NOT_ALLOWED");
+    };
+
+    override(reload_state, "is_pending", () => false);
+
+    const request = {foo: "bar"};
+    override(channel, "post", (opts) => {
+        assert.equal(opts.url, "/json/messages");
+        assert.equal(opts.data.foo, "bar");
+        const xhr = {
+            responseJSON: {
+                code: "TOPIC_WILDCARD_MENTION_NOT_ALLOWED",
+            },
+        };
+        opts.error(xhr, "bad request");
+    });
+
+    transmit.send_message(request, success, error);
+});
+
 run_test("reply_message_stream", ({override}) => {
     const social_stream_id = 555;
     stream_data.add_sub({
diff --git a/zerver/actions/message_edit.py b/zerver/actions/message_edit.py
index 2c18afdedd..b83e876907 100644
--- a/zerver/actions/message_edit.py
+++ b/zerver/actions/message_edit.py
@@ -22,7 +22,12 @@ from zerver.actions.message_send import (
 )
 from zerver.actions.uploads import check_attachment_reference_change
 from zerver.actions.user_topics import bulk_do_set_user_topic_visibility_policy
-from zerver.lib.exceptions import JsonableError, MessageMoveError
+from zerver.lib.exceptions import (
+    JsonableError,
+    MessageMoveError,
+    StreamWildcardMentionNotAllowedError,
+    TopicWildcardMentionNotAllowedError,
+)
 from zerver.lib.markdown import MessageRenderingResult, topic_links
 from zerver.lib.markdown import version as markdown_version
 from zerver.lib.mention import MentionBackend, MentionData, silent_mention_syntax_for_user
@@ -31,9 +36,10 @@ from zerver.lib.message import (
     bulk_access_messages,
     check_user_group_mention_allowed,
     normalize_body,
+    stream_wildcard_mention_allowed,
+    topic_wildcard_mention_allowed,
     truncate_topic,
     update_to_dict_cache,
-    wildcard_mention_allowed,
 )
 from zerver.lib.queue import queue_json_publish
 from zerver.lib.stream_subscription import get_active_subscriptions_for_stream_id
@@ -51,6 +57,7 @@ from zerver.lib.topic import (
     TOPIC_LINKS,
     TOPIC_NAME,
     messages_for_topic,
+    participants_for_topic,
     save_message_for_edit_use_case,
     update_edit_history,
     update_messages_for_topic_edit,
@@ -1274,12 +1281,19 @@ def check_update_message(
         )
         links_for_embed |= rendering_result.links_for_preview
 
-        if message.is_stream_message() and rendering_result.has_wildcard_mention():
+        if message.is_stream_message() and rendering_result.mentions_stream_wildcard:
             stream = access_stream_by_id(user_profile, message.recipient.type_id)[0]
-            if not wildcard_mention_allowed(message.sender, stream, message.realm):
-                raise JsonableError(
-                    _("You do not have permission to use wildcard mentions in this stream.")
-                )
+            if not stream_wildcard_mention_allowed(message.sender, stream, message.realm):
+                raise StreamWildcardMentionNotAllowedError
+
+        if message.is_stream_message() and rendering_result.mentions_topic_wildcard:
+            topic_participant_count = len(
+                participants_for_topic(message.realm.id, message.recipient.id, message.topic_name())
+            )
+            if not topic_wildcard_mention_allowed(
+                message.sender, topic_participant_count, message.realm
+            ):
+                raise TopicWildcardMentionNotAllowedError
 
         if rendering_result.mentions_user_group_ids:
             mentioned_group_ids = list(rendering_result.mentions_user_group_ids)
diff --git a/zerver/actions/message_send.py b/zerver/actions/message_send.py
index b51b1ed871..d335083cb6 100644
--- a/zerver/actions/message_send.py
+++ b/zerver/actions/message_send.py
@@ -39,7 +39,9 @@ from zerver.lib.exceptions import (
     JsonableError,
     MarkdownRenderingError,
     StreamDoesNotExistError,
+    StreamWildcardMentionNotAllowedError,
     StreamWithIDDoesNotExistError,
+    TopicWildcardMentionNotAllowedError,
     ZephyrMessageAlreadySentError,
 )
 from zerver.lib.markdown import MessageRenderingResult
@@ -52,9 +54,10 @@ from zerver.lib.message import (
     normalize_body,
     render_markdown,
     set_visibility_policy_possible,
+    stream_wildcard_mention_allowed,
+    topic_wildcard_mention_allowed,
     truncate_topic,
     visibility_policy_for_send_message,
-    wildcard_mention_allowed,
 )
 from zerver.lib.muted_users import get_muting_users
 from zerver.lib.notification_data import (
@@ -1710,12 +1713,18 @@ def check_message(
 
     if (
         stream is not None
-        and message_send_dict.rendering_result.has_wildcard_mention()
-        and not wildcard_mention_allowed(sender, stream, realm)
+        and message_send_dict.rendering_result.mentions_stream_wildcard
+        and not stream_wildcard_mention_allowed(sender, stream, realm)
     ):
-        raise JsonableError(
-            _("You do not have permission to use wildcard mentions in this stream.")
-        )
+        raise StreamWildcardMentionNotAllowedError
+
+    topic_participant_count = len(message_send_dict.topic_participant_user_ids)
+    if (
+        stream is not None
+        and message_send_dict.rendering_result.mentions_topic_wildcard
+        and not topic_wildcard_mention_allowed(sender, topic_participant_count, realm)
+    ):
+        raise TopicWildcardMentionNotAllowedError
 
     if message_send_dict.rendering_result.mentions_user_group_ids:
         mentioned_group_ids = list(message_send_dict.rendering_result.mentions_user_group_ids)
diff --git a/zerver/lib/exceptions.py b/zerver/lib/exceptions.py
index 4cc3b5d6ea..c2bb334b9f 100644
--- a/zerver/lib/exceptions.py
+++ b/zerver/lib/exceptions.py
@@ -47,6 +47,8 @@ class ErrorCode(Enum):
     REACTION_DOES_NOT_EXIST = auto()
     SERVER_NOT_READY = auto()
     MISSING_REMOTE_REALM = auto()
+    TOPIC_WILDCARD_MENTION_NOT_ALLOWED = auto()
+    STREAM_WILDCARD_MENTION_NOT_ALLOWED = auto()
 
 
 class JsonableError(Exception):
@@ -584,3 +586,27 @@ class MissingRemoteRealmError(JsonableError):  # nocoverage
     @override
     def msg_format() -> str:
         return _("Organization not registered")
+
+
+class StreamWildcardMentionNotAllowedError(JsonableError):
+    code: ErrorCode = ErrorCode.STREAM_WILDCARD_MENTION_NOT_ALLOWED
+
+    def __init__(self) -> None:
+        pass
+
+    @staticmethod
+    @override
+    def msg_format() -> str:
+        return _("You do not have permission to use stream wildcard mentions in this stream.")
+
+
+class TopicWildcardMentionNotAllowedError(JsonableError):
+    code: ErrorCode = ErrorCode.TOPIC_WILDCARD_MENTION_NOT_ALLOWED
+
+    def __init__(self) -> None:
+        pass
+
+    @staticmethod
+    @override
+    def msg_format() -> str:
+        return _("You do not have permission to use topic wildcard mentions in this topic.")
diff --git a/zerver/lib/markdown/__init__.py b/zerver/lib/markdown/__init__.py
index caaffc3c6f..d352d79bfc 100644
--- a/zerver/lib/markdown/__init__.py
+++ b/zerver/lib/markdown/__init__.py
@@ -134,9 +134,6 @@ class MessageRenderingResult:
     user_ids_with_alert_words: Set[int]
     potential_attachment_path_ids: List[str]
 
-    def has_wildcard_mention(self) -> bool:
-        return self.mentions_stream_wildcard or self.mentions_topic_wildcard
-
 
 @dataclass
 class DbData:
diff --git a/zerver/lib/message.py b/zerver/lib/message.py
index a4531d0c53..16c9b76818 100644
--- a/zerver/lib/message.py
+++ b/zerver/lib/message.py
@@ -1664,14 +1664,13 @@ def get_recent_private_conversations(user_profile: UserProfile) -> Dict[int, Dic
     return recipient_map
 
 
-def wildcard_mention_allowed(sender: UserProfile, stream: Stream, realm: Realm) -> bool:
-    # If there are fewer than Realm.WILDCARD_MENTION_THRESHOLD, we
-    # allow sending.  In the future, we may want to make this behavior
-    # a default, and also just allow explicitly setting whether this
-    # applies to a stream as an override.
-    if num_subscribers_for_stream_id(stream.id) <= Realm.WILDCARD_MENTION_THRESHOLD:
-        return True
-
+def wildcard_mention_policy_authorizes_user(sender: UserProfile, realm: Realm) -> bool:
+    """Helper function for 'topic_wildcard_mention_allowed' and
+    'stream_wildcard_mention_allowed' to check if the sender is allowed to use
+    wildcard mentions based on the 'wildcard_mention_policy' setting of that realm.
+    This check is used only if the participants count in the topic or the subscribers
+    count in the stream is greater than 'Realm.WILDCARD_MENTION_THRESHOLD'.
+    """
     if realm.wildcard_mention_policy == Realm.WILDCARD_MENTION_POLICY_NOBODY:
         return False
 
@@ -1693,6 +1692,24 @@ def wildcard_mention_allowed(sender: UserProfile, stream: Stream, realm: Realm)
     raise AssertionError("Invalid wildcard mention policy")
 
 
+def topic_wildcard_mention_allowed(
+    sender: UserProfile, topic_participant_count: int, realm: Realm
+) -> bool:
+    if topic_participant_count <= Realm.WILDCARD_MENTION_THRESHOLD:
+        return True
+    return wildcard_mention_policy_authorizes_user(sender, realm)
+
+
+def stream_wildcard_mention_allowed(sender: UserProfile, stream: Stream, realm: Realm) -> bool:
+    # If there are fewer than Realm.WILDCARD_MENTION_THRESHOLD, we
+    # allow sending.  In the future, we may want to make this behavior
+    # a default, and also just allow explicitly setting whether this
+    # applies to a stream as an override.
+    if num_subscribers_for_stream_id(stream.id) <= Realm.WILDCARD_MENTION_THRESHOLD:
+        return True
+    return wildcard_mention_policy_authorizes_user(sender, realm)
+
+
 def check_user_group_mention_allowed(sender: UserProfile, user_group_ids: List[int]) -> None:
     user_groups = UserGroup.objects.filter(id__in=user_group_ids).select_related(
         "can_mention_group"
diff --git a/zerver/openapi/zulip.yaml b/zerver/openapi/zulip.yaml
index adb409716d..82430b4413 100644
--- a/zerver/openapi/zulip.yaml
+++ b/zerver/openapi/zulip.yaml
@@ -6404,6 +6404,38 @@ paths:
                         description: |
                           A typical failed JSON response for when a direct message is sent to a user
                           that does not exist:
+                  - allOf:
+                      - $ref: "#/components/schemas/CodedError"
+                      - example:
+                          {
+                            "result": "error",
+                            "msg": "You do not have permission to use stream wildcard mentions in this stream.",
+                            "code": "STREAM_WILDCARD_MENTION_NOT_ALLOWED",
+                          }
+                        description: |
+                          An example JSON error response for when the message was rejected because
+                          of the organization's `wildcard_mention_policy` and large number of
+                          subscribers to the stream.
+
+                          **Changes**: New in Zulip 8.0 (feature level 229). Previously, this
+                          error returned the `"BAD_REQUEST"` code.
+                  - allOf:
+                      - $ref: "#/components/schemas/CodedError"
+                      - example:
+                          {
+                            "result": "error",
+                            "msg": "You do not have permission to use topic wildcard mentions in this topic.",
+                            "code": "TOPIC_WILDCARD_MENTION_NOT_ALLOWED",
+                          }
+                        description: |
+                          An example JSON error response for when the message was rejected because
+                          the message contains a topic wildcard mention, but the user doesn't have
+                          permission to use such a mention in this topic due to the
+                          `wildcard_mention_policy` (and large number of participants in this
+                          specific topic).
+
+                          **Changes**: New in Zulip 8.0 (feature level 229). Previously,
+                          `wildcard_mention_policy` was not enforced for topic mentions.
   /messages/{message_id}/history:
     get:
       operationId: get-message-history
@@ -7668,6 +7700,38 @@ paths:
                           dialog.
 
                           **Changes**: New in Zulip 7.0 (feature level 172).
+                  - allOf:
+                      - $ref: "#/components/schemas/CodedError"
+                      - example:
+                          {
+                            "result": "error",
+                            "msg": "You do not have permission to use stream wildcard mentions in this stream.",
+                            "code": "STREAM_WILDCARD_MENTION_NOT_ALLOWED",
+                          }
+                        description: |
+                          An example JSON error response for when the message was rejected because
+                          of the organization's `wildcard_mention_policy` and large number of
+                          subscribers to the stream.
+
+                          **Changes**: New in Zulip 8.0 (feature level 229). Previously, this
+                          error returned the `"BAD_REQUEST"` code.
+                  - allOf:
+                      - $ref: "#/components/schemas/CodedError"
+                      - example:
+                          {
+                            "result": "error",
+                            "msg": "You do not have permission to use topic wildcard mentions in this topic.",
+                            "code": "TOPIC_WILDCARD_MENTION_NOT_ALLOWED",
+                          }
+                        description: |
+                          An example JSON error response for when the message was rejected because
+                          the message contains a topic wildcard mention, but the user doesn't have
+                          permission to use such a mention in this topic due to the
+                          `wildcard_mention_policy` (and large number of participants in this
+                          specific topic).
+
+                          **Changes**: New in Zulip 8.0 (feature level 229). Previously,
+                          `wildcard_mention_policy` was not enforced for topic mentions.
     delete:
       operationId: delete-message
       summary: Delete a message
diff --git a/zerver/tests/test_message_edit.py b/zerver/tests/test_message_edit.py
index 8ff9a4fc24..9108ece213 100644
--- a/zerver/tests/test_message_edit.py
+++ b/zerver/tests/test_message_edit.py
@@ -2284,18 +2284,11 @@ class EditMessageTest(EditMessageTestCase):
             acting_user=None,
         )
 
-        with mock.patch("zerver.lib.message.num_subscribers_for_stream_id", return_value=17):
-            result = self.client_patch(
-                "/json/messages/" + str(message_id),
-                {
-                    "content": "Hello @**topic**",
-                },
-            )
-        self.assert_json_error(
-            result, "You do not have permission to use wildcard mentions in this stream."
-        )
-
-        with mock.patch("zerver.lib.message.num_subscribers_for_stream_id", return_value=14):
+        # Less than 'Realm.WILDCARD_MENTION_THRESHOLD' participants
+        participants_user_ids = set(range(1, 10))
+        with mock.patch(
+            "zerver.actions.message_edit.participants_for_topic", return_value=participants_user_ids
+        ):
             result = self.client_patch(
                 "/json/messages/" + str(message_id),
                 {
@@ -2304,9 +2297,27 @@ class EditMessageTest(EditMessageTestCase):
             )
         self.assert_json_success(result)
 
+        # More than 'Realm.WILDCARD_MENTION_THRESHOLD' participants.
+        participants_user_ids = set(range(1, 20))
+        with mock.patch(
+            "zerver.actions.message_edit.participants_for_topic", return_value=participants_user_ids
+        ):
+            result = self.client_patch(
+                "/json/messages/" + str(message_id),
+                {
+                    "content": "Hello @**topic**",
+                },
+            )
+        self.assert_json_error(
+            result, "You do not have permission to use topic wildcard mentions in this topic."
+        )
+
+        # Shiva is moderator
         self.login("shiva")
         message_id = self.send_stream_message(shiva, stream_name, "Hi everyone")
-        with mock.patch("zerver.lib.message.num_subscribers_for_stream_id", return_value=17):
+        with mock.patch(
+            "zerver.actions.message_edit.participants_for_topic", return_value=participants_user_ids
+        ):
             result = self.client_patch(
                 "/json/messages/" + str(message_id),
                 {
@@ -2389,7 +2400,7 @@ class EditMessageTest(EditMessageTestCase):
                 },
             )
         self.assert_json_error(
-            result, "You do not have permission to use wildcard mentions in this stream."
+            result, "You do not have permission to use stream wildcard mentions in this stream."
         )
 
         with mock.patch("zerver.lib.message.num_subscribers_for_stream_id", return_value=14):
diff --git a/zerver/tests/test_message_send.py b/zerver/tests/test_message_send.py
index 9b7332d206..e47128a28a 100644
--- a/zerver/tests/test_message_send.py
+++ b/zerver/tests/test_message_send.py
@@ -1783,11 +1783,14 @@ class StreamMessagesTest(ZulipTestCase):
         self.assertTrue(user_message.flags.mentioned)
 
     def send_and_verify_topic_wildcard_mention_message(
-        self, sender_name: str, test_fails: bool = False, sub_count: int = 16
+        self, sender_name: str, test_fails: bool = False, topic_participant_count: int = 20
     ) -> None:
         sender = self.example_user(sender_name)
         content = "@**topic** test topic wildcard mention"
-        with mock.patch("zerver.lib.message.num_subscribers_for_stream_id", return_value=sub_count):
+        participants_user_ids = set(range(topic_participant_count))
+        with mock.patch(
+            "zerver.actions.message_send.participants_for_topic", return_value=participants_user_ids
+        ):
             if not test_fails:
                 msg_id = self.send_stream_message(sender, "test_stream", content)
                 result = self.api_get(sender, "/api/v1/messages/" + str(msg_id))
@@ -1796,7 +1799,7 @@ class StreamMessagesTest(ZulipTestCase):
             else:
                 with self.assertRaisesRegex(
                     JsonableError,
-                    "You do not have permission to use wildcard mentions in this stream.",
+                    "You do not have permission to use topic wildcard mentions in this topic.",
                 ):
                     self.send_stream_message(sender, "test_stream", content)
 
@@ -1828,8 +1831,8 @@ class StreamMessagesTest(ZulipTestCase):
             acting_user=None,
         )
         self.send_and_verify_topic_wildcard_mention_message("polonius", test_fails=True)
-        # There is no restriction on small streams.
-        self.send_and_verify_topic_wildcard_mention_message("polonius", sub_count=10)
+        # There is no restriction on topics with less than 'Realm.WILDCARD_MENTION_THRESHOLD' participants.
+        self.send_and_verify_topic_wildcard_mention_message("polonius", topic_participant_count=10)
         self.send_and_verify_topic_wildcard_mention_message("cordelia")
 
         do_set_realm_property(
@@ -1846,7 +1849,7 @@ class StreamMessagesTest(ZulipTestCase):
         cordelia.date_joined = timezone_now()
         cordelia.save()
         self.send_and_verify_topic_wildcard_mention_message("cordelia", test_fails=True)
-        self.send_and_verify_topic_wildcard_mention_message("cordelia", sub_count=10)
+        self.send_and_verify_topic_wildcard_mention_message("cordelia", topic_participant_count=10)
         # Administrators and moderators can use wildcard mentions even if they are new.
         self.send_and_verify_topic_wildcard_mention_message("iago")
         self.send_and_verify_topic_wildcard_mention_message("shiva")
@@ -1862,7 +1865,7 @@ class StreamMessagesTest(ZulipTestCase):
             acting_user=None,
         )
         self.send_and_verify_topic_wildcard_mention_message("cordelia", test_fails=True)
-        self.send_and_verify_topic_wildcard_mention_message("cordelia", sub_count=10)
+        self.send_and_verify_topic_wildcard_mention_message("cordelia", topic_participant_count=10)
         self.send_and_verify_topic_wildcard_mention_message("shiva")
 
         cordelia.date_joined = timezone_now()
@@ -1871,15 +1874,15 @@ class StreamMessagesTest(ZulipTestCase):
             realm, "wildcard_mention_policy", Realm.WILDCARD_MENTION_POLICY_ADMINS, acting_user=None
         )
         self.send_and_verify_topic_wildcard_mention_message("shiva", test_fails=True)
-        # There is no restriction on small streams.
-        self.send_and_verify_topic_wildcard_mention_message("shiva", sub_count=10)
+        # There is no restriction on topics with less than 'Realm.WILDCARD_MENTION_THRESHOLD' participants.
+        self.send_and_verify_topic_wildcard_mention_message("shiva", topic_participant_count=10)
         self.send_and_verify_topic_wildcard_mention_message("iago")
 
         do_set_realm_property(
             realm, "wildcard_mention_policy", Realm.WILDCARD_MENTION_POLICY_NOBODY, acting_user=None
         )
         self.send_and_verify_topic_wildcard_mention_message("iago", test_fails=True)
-        self.send_and_verify_topic_wildcard_mention_message("iago", sub_count=10)
+        self.send_and_verify_topic_wildcard_mention_message("iago", topic_participant_count=10)
 
     def send_and_verify_stream_wildcard_mention_message(
         self, sender_name: str, test_fails: bool = False, sub_count: int = 16
@@ -1895,7 +1898,7 @@ class StreamMessagesTest(ZulipTestCase):
             else:
                 with self.assertRaisesRegex(
                     JsonableError,
-                    "You do not have permission to use wildcard mentions in this stream.",
+                    "You do not have permission to use stream wildcard mentions in this stream.",
                 ):
                     self.send_stream_message(sender, "test_stream", content)