diff --git a/web/chat/chat-input-bar.react.js b/web/chat/chat-input-bar.react.js
--- a/web/chat/chat-input-bar.react.js
+++ b/web/chat/chat-input-bar.react.js
@@ -17,6 +17,7 @@
   getMentionTypeaheadUserSuggestions,
   getTypeaheadRegexMatches,
   getUserMentionsCandidates,
+  getMentionTypeaheadChatSuggestions,
   type MentionTypeaheadSuggestionItem,
   type TypeaheadMatchedStrings,
 } from 'lib/shared/mention-utils.js';
@@ -27,6 +28,8 @@
   threadFrozenDueToViewerBlock,
   threadActualMembers,
   checkIfDefaultMembersAreVoiced,
+  useThreadChatMentionCandidates,
+  useThreadChatMentionSearchIndex,
 } from 'lib/shared/thread-utils.js';
 import type { CalendarQuery } from 'lib/types/entry-types.js';
 import type { LoadingStatus } from 'lib/types/loading-types.js';
@@ -578,6 +581,9 @@
     const dispatchActionPromise = useDispatchActionPromise();
     const callJoinThread = useServerCall(joinThread);
     const userSearchIndex = useSelector(userStoreMentionSearchIndex);
+    const chatMentionSearchIndex = useThreadChatMentionSearchIndex(
+      props.threadInfo,
+    );
 
     const { parentThreadID } = props.threadInfo;
     const parentThreadInfo = useSelector(state =>
@@ -589,6 +595,10 @@
       parentThreadInfo,
     );
 
+    const chatMentionCandidates = useThreadChatMentionCandidates(
+      props.threadInfo,
+    );
+
     const typeaheadRegexMatches = React.useMemo(
       () =>
         getTypeaheadRegexMatches(
@@ -619,29 +629,39 @@
         const setter = props.inputState.setTypeaheadState;
         setter({
           frozenUserMentionsCandidates: userMentionsCandidates,
+          frozenChatMentionsCandidates: chatMentionCandidates,
         });
       }
     }, [
       userMentionsCandidates,
       props.inputState.setTypeaheadState,
       props.inputState.typeaheadState.keepUpdatingThreadMembers,
+      chatMentionCandidates,
     ]);
 
-    const suggestedUsers = React.useMemo(() => {
+    const suggestions = React.useMemo(() => {
       if (!typeaheadMatchedStrings) {
         return [];
       }
-      return getMentionTypeaheadUserSuggestions(
+      const suggestedUsers = getMentionTypeaheadUserSuggestions(
         userSearchIndex,
         props.inputState.typeaheadState.frozenUserMentionsCandidates,
         viewerID,
         typeaheadMatchedStrings.textPrefix,
       );
+      const suggestedChats = getMentionTypeaheadChatSuggestions(
+        chatMentionSearchIndex,
+        props.inputState.typeaheadState.frozenChatMentionsCandidates,
+        typeaheadMatchedStrings.textPrefix,
+      );
+      return [...suggestedUsers, ...suggestedChats];
     }, [
+      typeaheadMatchedStrings,
       userSearchIndex,
       props.inputState.typeaheadState.frozenUserMentionsCandidates,
+      props.inputState.typeaheadState.frozenChatMentionsCandidates,
       viewerID,
-      typeaheadMatchedStrings,
+      chatMentionSearchIndex,
     ]);
 
     return (
@@ -657,7 +677,7 @@
         dispatchActionPromise={dispatchActionPromise}
         joinThread={callJoinThread}
         typeaheadMatchedStrings={typeaheadMatchedStrings}
-        suggestions={suggestedUsers}
+        suggestions={suggestions}
         parentThreadInfo={parentThreadInfo}
       />
     );
diff --git a/web/input/input-state-container.react.js b/web/input/input-state-container.react.js
--- a/web/input/input-state-container.react.js
+++ b/web/input/input-state-container.react.js
@@ -176,6 +176,7 @@
       canBeVisible: false,
       keepUpdatingThreadMembers: true,
       frozenUserMentionsCandidates: [],
+      frozenChatMentionsCandidates: {},
       moveChoiceUp: null,
       moveChoiceDown: null,
       close: null,
diff --git a/web/input/input-state.js b/web/input/input-state.js
--- a/web/input/input-state.js
+++ b/web/input/input-state.js
@@ -9,7 +9,11 @@
   type MediaMissionStep,
 } from 'lib/types/media-types.js';
 import type { RawTextMessageInfo } from 'lib/types/messages/text.js';
-import type { ThreadInfo, RelativeMemberInfo } from 'lib/types/thread-types.js';
+import type {
+  ThreadInfo,
+  RelativeMemberInfo,
+  ChatMentionCandidates,
+} from 'lib/types/thread-types.js';
 
 export type PendingMultimediaUpload = {
   +localID: string,
@@ -43,6 +47,7 @@
   +canBeVisible: boolean,
   +keepUpdatingThreadMembers: boolean,
   +frozenUserMentionsCandidates: $ReadOnlyArray<RelativeMemberInfo>,
+  +frozenChatMentionsCandidates: ChatMentionCandidates,
   +moveChoiceUp: ?() => void,
   +moveChoiceDown: ?() => void,
   +close: ?() => void,
diff --git a/web/utils/typeahead-utils.js b/web/utils/typeahead-utils.js
--- a/web/utils/typeahead-utils.js
+++ b/web/utils/typeahead-utils.js
@@ -8,11 +8,13 @@
   getNewTextAndSelection,
   type MentionTypeaheadSuggestionItem,
   type TypeaheadTooltipActionItem,
+  encodeChatMentionText,
 } from 'lib/shared/mention-utils.js';
 import { validChatNameRegexString } from 'lib/shared/thread-utils.js';
 import { stringForUserExplicit } from 'lib/shared/user-utils.js';
 import type { SetState } from 'lib/types/hook-types.js';
 
+import ThreadAvatar from '../avatars/thread-avatar.react.js';
 import UserAvatar from '../avatars/user-avatar.react.js';
 import { typeaheadStyle } from '../chat/chat-constants.js';
 import css from '../chat/typeahead-tooltip.css';
@@ -120,6 +122,29 @@
           userInfo: suggestedUser,
         },
       });
+    } else if (suggestion.type === 'chat') {
+      const suggestedChat = suggestion.threadInfo;
+      const mentionText = `@[[${suggestedChat.id}:${encodeChatMentionText(
+        suggestedChat.uiName,
+      )}]]`;
+      actions.push({
+        key: suggestedChat.id,
+        execute: () => {
+          const { newText, newSelectionStart } = getNewTextAndSelection(
+            textBeforeAtSymbol,
+            inputStateDraft,
+            textPrefix,
+            mentionText,
+          );
+
+          inputStateSetDraft(newText);
+          inputStateSetTextCursorPosition(newSelectionStart);
+        },
+        actionButtonContent: {
+          type: 'chat',
+          threadInfo: suggestedChat,
+        },
+      });
     }
   }
   return actions;
@@ -155,6 +180,15 @@
         <UserAvatar size="small" userID={actionButtonContent.userInfo.id} />
       );
       typeaheadButtonText = `@${stringForUserExplicit(suggestedUser)}`;
+    } else if (actionButtonContent.type === 'chat') {
+      const suggestedChat = actionButtonContent.threadInfo;
+      avatarComponent = (
+        <ThreadAvatar
+          size="small"
+          threadInfo={actionButtonContent.threadInfo}
+        />
+      );
+      typeaheadButtonText = `@${suggestedChat.uiName}`;
     }
 
     return (