diff --git a/web/modals/threads/members/add-members-group.react.js b/web/modals/threads/members/add-members-group.react.js
--- a/web/modals/threads/members/add-members-group.react.js
+++ b/web/modals/threads/members/add-members-group.react.js
@@ -8,7 +8,7 @@
 import css from './members-modal.css';
 
 type AddMemberItemGroupProps = {
-  +header: string,
+  +header: ?string,
   +userInfos: $ReadOnlyArray<UserListItem>,
   +onUserClick: (userID: string) => void,
   +usersAdded: $ReadOnlySet<string>,
@@ -32,10 +32,13 @@
       )),
     [onUserClick, sortedUserInfos, usersAdded],
   );
+  const headerComponent = header ? (
+    <div className={css.addMemberItemsGroupHeader}>{header}:</div>
+  ) : null;
 
   return (
     <>
-      <div className={css.addMemberItemsGroupHeader}>{header}:</div>
+      {headerComponent}
       {userInfosComponents}
     </>
   );
diff --git a/web/modals/threads/members/add-members-list.react.js b/web/modals/threads/members/add-members-list.react.js
--- a/web/modals/threads/members/add-members-list.react.js
+++ b/web/modals/threads/members/add-members-list.react.js
@@ -12,10 +12,16 @@
   +userListItems: $ReadOnlyArray<UserListItem>,
   +pendingUsersToAdd: $ReadOnlySet<string>,
   +switchUser: string => void,
+  +hasParentThread: boolean,
 };
 
 function AddMembersList(props: Props): React.Node {
-  const { userListItems, pendingUsersToAdd, switchUser } = props;
+  const {
+    userListItems,
+    pendingUsersToAdd,
+    switchUser,
+    hasParentThread,
+  } = props;
 
   const usersAvailableToAdd = React.useMemo(
     () => userListItems.filter(user => !user.alertText),
@@ -27,13 +33,13 @@
     [usersAvailableToAdd],
   );
 
-  const membersInParentThread = React.useMemo(
-    () =>
-      groupedAvailableUsersList['undefined']
-        ? ['Users in parent channel', groupedAvailableUsersList['undefined']]
-        : undefined,
-    [groupedAvailableUsersList],
-  );
+  const membersInParentThread = React.useMemo(() => {
+    if (!groupedAvailableUsersList['undefined']) {
+      return;
+    }
+    const label = hasParentThread ? 'Users in parent channel' : null;
+    return [label, groupedAvailableUsersList['undefined']];
+  }, [groupedAvailableUsersList, hasParentThread]);
 
   const membersNotInParentThread = React.useMemo(
     () =>
diff --git a/web/modals/threads/members/add-members-modal.react.js b/web/modals/threads/members/add-members-modal.react.js
--- a/web/modals/threads/members/add-members-modal.react.js
+++ b/web/modals/threads/members/add-members-modal.react.js
@@ -143,6 +143,7 @@
           userListItems={userSearchResults}
           switchUser={onSwitchUser}
           pendingUsersToAdd={pendingUsersToAdd}
+          hasParentThread={!!threadInfo.parentThreadID}
         />
       </div>
       <div className={css.addMembersFooter}>