diff --git a/lib/selectors/nav-selectors.js b/lib/selectors/nav-selectors.js
--- a/lib/selectors/nav-selectors.js
+++ b/lib/selectors/nav-selectors.js
@@ -6,6 +6,7 @@
 import { useResolvableNames } from '../hooks/names-cache.js';
 import SearchIndex from '../shared/search-index.js';
 import { threadTypeIsPrivate } from '../shared/threads/thread-specs.js';
+import { ensNameForFarcasterUsername } from '../shared/user-utils.js';
 import type { Platform } from '../types/device-types.js';
 import {
   type CalendarQuery,
@@ -81,16 +82,24 @@
 // recaculation just once for every update of the underlying Redux data.
 const useResolvableNamesOptions = { allAtOnce: true };
 
+type SearchIndexUserInfo = {
+  +id: string,
+  +username: ?string,
+  +fid?: ?string,
+  +farcasterUsername?: ?string,
+  ...
+};
+
 function useUserSearchIndex(
   userInfos: $ReadOnlyArray<UserInfo | RelativeMemberInfo>,
 ): SearchIndex {
-  const membersWithENSNames = useResolvableNames(
+  const membersWithENSNames = useResolvableNames<SearchIndexUserInfo>(
     userInfos,
     useResolvableNamesOptions,
   );
 
   const memberMap = React.useMemo(() => {
-    const result = new Map<string, UserInfo | RelativeMemberInfo>();
+    const result = new Map<string, SearchIndexUserInfo>();
     for (const userInfo of membersWithENSNames) {
       result.set(userInfo.id, userInfo);
     }
@@ -114,6 +123,17 @@
         searchTextArray.push(resolvedUsername);
       }
 
+      const resolvedFarcasterName = resolvedUserInfo?.farcasterUsername;
+      if (
+        resolvedFarcasterName &&
+        resolvedFarcasterName !== rawUsername &&
+        resolvedFarcasterName !== resolvedUsername
+      ) {
+        searchTextArray.push(
+          ensNameForFarcasterUsername(resolvedFarcasterName),
+        );
+      }
+
       searchIndex.addEntry(userInfo.id, searchTextArray.join(' '));
     }
 
diff --git a/lib/shared/search-utils.js b/lib/shared/search-utils.js
--- a/lib/shared/search-utils.js
+++ b/lib/shared/search-utils.js
@@ -26,6 +26,7 @@
 import {
   useUsersSupportFarcasterDCs,
   useUsersSupportThickThreads,
+  useGetCommFCUsersForFIDs,
 } from '../hooks/user-identities-hooks.js';
 import { useIdentitySearch } from '../identity-search/identity-search-context.js';
 import { useLegacyAshoatKeyserverCall } from '../keyserver-conn/legacy-keyserver-call.js';
@@ -364,6 +365,7 @@
 
   const usersSupportFarcasterDCs = useUsersSupportFarcasterDCs();
   const usersSupportThickThreads = useUsersSupportThickThreads();
+  const getFarcasterUsers = useGetCommFCUsersForFIDs();
 
   const [potentialMembers, setPotentialMembers] = React.useState<
     UserListItem[],
@@ -371,17 +373,35 @@
   React.useEffect(() => {
     void (async () => {
       const usersIDs = sortedMembers.map(user => user.id);
+      const fids = usersIDs.map(extractFIDFromUserID).filter(Boolean);
+      const fcUserInfos = await getFarcasterUsers(fids);
+      const fcCommUserIDs = Array.from(fcUserInfos.keys());
+
+      const userIDsSet = new Set([...usersIDs, ...fcCommUserIDs]);
+      const allUserIDs = [...userIDsSet];
+
       const [thickThreadUsers, farcasterUsers] = await Promise.all([
-        usersSupportThickThreads(usersIDs),
-        usersSupportFarcasterDCs(usersIDs),
+        usersSupportThickThreads(allUserIDs),
+        usersSupportFarcasterDCs(allUserIDs),
       ]);
       const usersWithProtocol = sortedMembers
         .map(member => {
+          let memberID = member.id;
+          const fid = extractFIDFromUserID(memberID);
+          if (fid) {
+            const fcCommUser = fcUserInfos.get(fid);
+            if (fcCommUser) {
+              // replace Farcaster-only userID with actual Comm
+              // userID when possible
+              memberID = fcCommUser.userID;
+            }
+          }
+
           const supportedProtocols: Array<ProtocolName> = [];
-          if (thickThreadUsers.get(member.id)) {
+          if (thickThreadUsers.get(memberID)) {
             supportedProtocols.push(protocolNames.COMM_DM);
           }
-          if (viewerID !== member.id && farcasterUsers.get(member.id)) {
+          if (viewerID !== memberID && farcasterUsers.get(memberID)) {
             supportedProtocols.push(protocolNames.FARCASTER_DC);
           }
           if (
@@ -392,6 +412,7 @@
           }
           return {
             ...member,
+            id: memberID,
             supportedProtocols: [...supportedProtocols],
           };
         })
@@ -403,6 +424,7 @@
     sortedMembers,
     usersSupportFarcasterDCs,
     usersSupportThickThreads,
+    getFarcasterUsers,
     viewerID,
   ]);
 
diff --git a/lib/types/user-types.js b/lib/types/user-types.js
--- a/lib/types/user-types.js
+++ b/lib/types/user-types.js
@@ -126,4 +126,5 @@
   },
   +avatar?: ?ClientAvatar,
   +supportedProtocols: Array<ProtocolName>,
+  +farcasterUsername?: ?string,
 };
diff --git a/native/components/user-list.react.js b/native/components/user-list.react.js
--- a/native/components/user-list.react.js
+++ b/native/components/user-list.react.js
@@ -37,7 +37,7 @@
   }
 
   static keyExtractor = (userInfo: UserListItem): string => {
-    return userInfo.id;
+    return `${userInfo.id}:${userInfo.username}`;
   };
 
   renderItem = (row: { +item: UserListItem, ... }): React.Node => {
diff --git a/web/chat/chat-thread-composer.react.js b/web/chat/chat-thread-composer.react.js
--- a/web/chat/chat-thread-composer.react.js
+++ b/web/chat/chat-thread-composer.react.js
@@ -200,7 +200,10 @@
           icon = <ProtocolIcon protocol="Farcaster DC" size={23} />;
         }
         return (
-          <li key={userSearchResult.id} className={css.searchResultsItem}>
+          <li
+            key={`${userSearchResult.id}:${userSearchResult.username}`}
+            className={css.searchResultsItem}
+          >
             <Button
               variant="text"
               onClick={() => onSelectUserFromSearch(userSearchResult)}