diff --git a/lib/shared/notif-utils.js b/lib/shared/notif-utils.js
--- a/lib/shared/notif-utils.js
+++ b/lib/shared/notif-utils.js
@@ -17,7 +17,9 @@
 import {
   ET,
   getEntityTextAsString,
+  pluralizeEntityText,
   type EntityText,
+  type UserEntity,
 } from '../utils/entity-text';
 import { promiseAll } from '../utils/promises';
 import { trimText } from '../utils/text-utils';
@@ -96,7 +98,7 @@
   +threadType: ThreadType,
   +parentThreadInfo: ThreadInfo,
   +childThreadName: ?string,
-  +childThreadUIName: EntityText | string,
+  +childThreadUIName: string | $ReadOnlyArray<UserEntity>,
 };
 function notifTextsForSubthreadCreation(
   input: NotifTextsForSubthreadCreationInput,
@@ -179,10 +181,15 @@
     );
     return notifString;
   };
+  const unresolvedTitle = unresolvedNotifTexts.title;
+  const pluralizedTitle =
+    typeof unresolvedTitle === 'string'
+      ? unresolvedTitle
+      : pluralizeEntityText(unresolvedTitle.map(entity => [entity]));
   let promises = {
     merged: resolveToString(unresolvedNotifTexts.merged),
     body: resolveToString(unresolvedNotifTexts.body),
-    title: resolveToString(unresolvedNotifTexts.title),
+    title: resolveToString(pluralizedTitle),
   };
   if (unresolvedNotifTexts.prefix) {
     promises = {
diff --git a/lib/types/notif-types.js b/lib/types/notif-types.js
--- a/lib/types/notif-types.js
+++ b/lib/types/notif-types.js
@@ -1,11 +1,11 @@
 // @flow
 
-import type { EntityText } from '../utils/entity-text';
+import type { EntityText, UserEntity } from '../utils/entity-text';
 
 export type NotifTexts = {
   +merged: string | EntityText,
   +body: string | EntityText,
-  +title: string | EntityText,
+  +title: string | $ReadOnlyArray<UserEntity>,
   +prefix?: string | EntityText,
 };