diff --git a/lib/Chat/ChatManager.php b/lib/Chat/ChatManager.php
index a4c349cbc1ba..fc145c8858d7 100644
--- a/lib/Chat/ChatManager.php
+++ b/lib/Chat/ChatManager.php
@@ -177,17 +177,20 @@ public function addSystemMessage(
 			if ($sendNotifications) {
 				/** @var ?IComment $captionComment */
 				$captionComment = null;
-				$alreadyNotifiedUsers = $usersDirectlyMentioned = [];
+				$alreadyNotifiedUsers = $usersDirectlyMentioned = $federatedUsersDirectlyMentioned = [];
 				if ($messageType === 'file_shared') {
 					if (isset($messageDecoded['parameters']['metaData']['caption'])) {
 						$captionComment = clone $comment;
 						$captionComment->setMessage($messageDecoded['parameters']['metaData']['caption'], self::MAX_CHAT_LENGTH);
 						$usersDirectlyMentioned = $this->notifier->getMentionedUserIds($captionComment);
+						$federatedUsersDirectlyMentioned = $this->notifier->getMentionedCloudIds($captionComment);
 					}
 					if ($replyTo instanceof IComment) {
 						$alreadyNotifiedUsers = $this->notifier->notifyReplyToAuthor($chat, $comment, $replyTo, $silent);
 						if ($replyTo->getActorType() === Attendee::ACTOR_USERS) {
 							$usersDirectlyMentioned[] = $replyTo->getActorId();
+						} elseif ($replyTo->getActorType() === Attendee::ACTOR_FEDERATED_USERS) {
+							$federatedUsersDirectlyMentioned[] = $replyTo->getActorId();
 						}
 					}
 				}
@@ -195,7 +198,10 @@ public function addSystemMessage(
 				$alreadyNotifiedUsers = $this->notifier->notifyMentionedUsers($chat, $captionComment ?? $comment, $alreadyNotifiedUsers, $silent);
 				if (!empty($alreadyNotifiedUsers)) {
 					$userIds = array_column($alreadyNotifiedUsers, 'id');
-					$this->participantService->markUsersAsMentioned($chat, $userIds, (int) $comment->getId(), $usersDirectlyMentioned);
+					$this->participantService->markUsersAsMentioned($chat, Attendee::ACTOR_USERS, $userIds, (int) $comment->getId(), $usersDirectlyMentioned);
+				}
+				if (!empty($federatedUsersDirectlyMentioned)) {
+					$this->participantService->markUsersAsMentioned($chat, Attendee::ACTOR_FEDERATED_USERS, $federatedUsersDirectlyMentioned, (int) $comment->getId(), $federatedUsersDirectlyMentioned);
 				}
 
 				$this->notifier->notifyOtherParticipant($chat, $comment, [], $silent);
@@ -326,17 +332,23 @@ public function sendMessage(Room $chat, ?Participant $participant, string $actor
 
 			$alreadyNotifiedUsers = [];
 			$usersDirectlyMentioned = $this->notifier->getMentionedUserIds($comment);
+			$federatedUsersDirectlyMentioned = $this->notifier->getMentionedCloudIds($comment);
 			if ($replyTo instanceof IComment) {
 				$alreadyNotifiedUsers = $this->notifier->notifyReplyToAuthor($chat, $comment, $replyTo, $silent);
 				if ($replyTo->getActorType() === Attendee::ACTOR_USERS) {
 					$usersDirectlyMentioned[] = $replyTo->getActorId();
+				} elseif ($replyTo->getActorType() === Attendee::ACTOR_FEDERATED_USERS) {
+					$federatedUsersDirectlyMentioned[] = $replyTo->getActorId();
 				}
 			}
 
 			$alreadyNotifiedUsers = $this->notifier->notifyMentionedUsers($chat, $comment, $alreadyNotifiedUsers, $silent);
 			if (!empty($alreadyNotifiedUsers)) {
 				$userIds = array_column($alreadyNotifiedUsers, 'id');
-				$this->participantService->markUsersAsMentioned($chat, $userIds, (int) $comment->getId(), $usersDirectlyMentioned);
+				$this->participantService->markUsersAsMentioned($chat, Attendee::ACTOR_USERS, $userIds, (int) $comment->getId(), $usersDirectlyMentioned);
+			}
+			if (!empty($federatedUsersDirectlyMentioned)) {
+				$this->participantService->markUsersAsMentioned($chat, Attendee::ACTOR_FEDERATED_USERS, $federatedUsersDirectlyMentioned, (int) $comment->getId(), $federatedUsersDirectlyMentioned);
 			}
 
 			// User was not mentioned, send a normal notification
@@ -561,12 +573,16 @@ public function editMessage(Room $chat, IComment $comment, Participant $particip
 
 			if (!empty($addedMentions)) {
 				$usersDirectlyMentionedAfter = $this->notifier->getMentionedUserIds($comment);
+				$federatedUsersDirectlyMentionedAfter = $this->notifier->getMentionedCloudIds($comment);
 				$addedUsersDirectMentioned = array_diff($usersDirectlyMentionedAfter, $usersDirectlyMentionedBefore);
 
 				$alreadyNotifiedUsers = $this->notifier->notifyMentionedUsers($chat, $comment, $usersToNotifyBefore, silent: false);
 				if (!empty($alreadyNotifiedUsers)) {
 					$userIds = array_column($alreadyNotifiedUsers, 'id');
-					$this->participantService->markUsersAsMentioned($chat, $userIds, (int) $comment->getId(), $addedUsersDirectMentioned);
+					$this->participantService->markUsersAsMentioned($chat, Attendee::ACTOR_USERS, $userIds, (int) $comment->getId(), $addedUsersDirectMentioned);
+				}
+				if (!empty($federatedUsersDirectlyMentionedAfter)) {
+					$this->participantService->markUsersAsMentioned($chat, Attendee::ACTOR_FEDERATED_USERS, $federatedUsersDirectlyMentionedAfter, (int) $comment->getId(), $federatedUsersDirectlyMentionedAfter);
 				}
 			}
 		}
diff --git a/lib/Chat/Notifier.php b/lib/Chat/Notifier.php
index 8ba24bd1547c..7d6393dda466 100644
--- a/lib/Chat/Notifier.php
+++ b/lib/Chat/Notifier.php
@@ -202,11 +202,21 @@ private function addMentionAllToList(Room $chat, array $list): array {
 	 * @psalm-return array<int, array{id: string, type: string, reason: string}>
 	 */
 	public function notifyReplyToAuthor(Room $chat, IComment $comment, IComment $replyTo, bool $silent): array {
-		if ($replyTo->getActorType() !== Attendee::ACTOR_USERS) {
-			// No reply notification when the replyTo-author was not a user
+		if ($replyTo->getActorType() !== Attendee::ACTOR_USERS && $replyTo->getActorType() !== Attendee::ACTOR_FEDERATED_USERS) {
+			// No reply notification when the replyTo-author was not a user or federated user
 			return [];
 		}
 
+		if ($replyTo->getActorType() === Attendee::ACTOR_FEDERATED_USERS) {
+			return [
+				[
+					'id' => $replyTo->getActorId(),
+					'type' => $replyTo->getActorType(),
+					'reason' => 'reply',
+				],
+			];
+		}
+
 		if (!$this->shouldMentionedUserBeNotified($replyTo->getActorId(), $comment, $chat)) {
 			return [];
 		}
@@ -407,6 +417,19 @@ public function getMentionedUserIds(IComment $comment): array {
 		}, $mentionedUsers);
 	}
 
+	/**
+	 * Returns the cloud IDs of the federated users mentioned in the given comment.
+	 *
+	 * @param IComment $comment
+	 * @return string[] the mentioned cloud IDs
+	 */
+	public function getMentionedCloudIds(IComment $comment): array {
+		$mentionedFederatedUsers = $this->getMentionedFederatedUsers($comment);
+		return array_map(static function ($mentionedUser) {
+			return $mentionedUser['id'];
+		}, $mentionedFederatedUsers);
+	}
+
 	/**
 	 * @param IComment $comment
 	 * @return array[]
@@ -427,7 +450,34 @@ private function getMentionedUsers(IComment $comment): array {
 
 			$mentionedUsers[] = [
 				'id' => $mention['id'],
-				'type' => 'users',
+				'type' => Attendee::ACTOR_USERS,
+				'reason' => 'direct',
+			];
+		}
+		return $mentionedUsers;
+	}
+
+	/**
+	 * @param IComment $comment
+	 * @return array[]
+	 * @psalm-return array<int, array{type: string, id: string, reason: string}>
+	 */
+	private function getMentionedFederatedUsers(IComment $comment): array {
+		$mentions = $comment->getMentions();
+
+		if (empty($mentions)) {
+			return [];
+		}
+
+		$mentionedUsers = [];
+		foreach ($mentions as $mention) {
+			if ($mention['type'] !== 'federated_user') {
+				continue;
+			}
+
+			$mentionedUsers[] = [
+				'id' => $mention['id'],
+				'type' => Attendee::ACTOR_FEDERATED_USERS,
 				'reason' => 'direct',
 			];
 		}
diff --git a/lib/Service/ParticipantService.php b/lib/Service/ParticipantService.php
index 6d0711ed6c31..7ea81e69c7e0 100644
--- a/lib/Service/ParticipantService.php
+++ b/lib/Service/ParticipantService.php
@@ -1283,28 +1283,26 @@ public function updateCallFlags(Room $room, Participant $participant, int $flags
 	}
 
 	/**
-	 * @param Room $room
-	 * @param string[] $userIds
-	 * @param int $messageId
+	 * @param string[] $actorIds
 	 * @param string[] $usersDirectlyMentioned
 	 */
-	public function markUsersAsMentioned(Room $room, array $userIds, int $messageId, array $usersDirectlyMentioned): void {
+	public function markUsersAsMentioned(Room $room, string $actorType, array $actorIds, int $messageId, array $actorsDirectlyMentioned): void {
 		$update = $this->connection->getQueryBuilder();
 		$update->update('talk_attendees')
 			->set('last_mention_message', $update->createNamedParameter($messageId, IQueryBuilder::PARAM_INT))
 			->where($update->expr()->eq('room_id', $update->createNamedParameter($room->getId(), IQueryBuilder::PARAM_INT)))
-			->andWhere($update->expr()->eq('actor_type', $update->createNamedParameter(Attendee::ACTOR_USERS)))
-			->andWhere($update->expr()->in('actor_id', $update->createNamedParameter($userIds, IQueryBuilder::PARAM_STR_ARRAY)))
+			->andWhere($update->expr()->eq('actor_type', $update->createNamedParameter($actorType)))
+			->andWhere($update->expr()->in('actor_id', $update->createNamedParameter($actorIds, IQueryBuilder::PARAM_STR_ARRAY)))
 			->andWhere($update->expr()->lt('last_mention_message', $update->createNamedParameter($messageId, IQueryBuilder::PARAM_INT)));
 		$update->executeStatement();
 
-		if (!empty($usersDirectlyMentioned)) {
+		if (!empty($actorsDirectlyMentioned)) {
 			$update = $this->connection->getQueryBuilder();
 			$update->update('talk_attendees')
 				->set('last_mention_direct', $update->createNamedParameter($messageId, IQueryBuilder::PARAM_INT))
 				->where($update->expr()->eq('room_id', $update->createNamedParameter($room->getId(), IQueryBuilder::PARAM_INT)))
-				->andWhere($update->expr()->eq('actor_type', $update->createNamedParameter(Attendee::ACTOR_USERS)))
-				->andWhere($update->expr()->in('actor_id', $update->createNamedParameter($usersDirectlyMentioned, IQueryBuilder::PARAM_STR_ARRAY)))
+				->andWhere($update->expr()->eq('actor_type', $update->createNamedParameter($actorType)))
+				->andWhere($update->expr()->in('actor_id', $update->createNamedParameter($actorsDirectlyMentioned, IQueryBuilder::PARAM_STR_ARRAY)))
 				->andWhere($update->expr()->lt('last_mention_direct', $update->createNamedParameter($messageId, IQueryBuilder::PARAM_INT)));
 			$update->executeStatement();
 		}