diff --git a/db/db.go b/db/db.go
index d2d5800..3879cd7 100644
--- a/db/db.go
+++ b/db/db.go
@@ -39,3 +39,25 @@ func AddChat(chatID int64) error {
 	}
 	return result.Err()
 }
+
+func AddUserInChat(chatID int64, username string) error {
+	if err := AddChat(chatID); err != nil {
+		return err
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	client, err := mongo.Connect(ctx, options.Client().ApplyURI(cfg.MongoURL))
+	if err != nil {
+		return err
+	}
+
+	collection := client.Database(cfg.DBName).Collection(cfg.ChatsCollectionName)
+	_, err = collection.UpdateOne(
+		ctx,
+		bson.E{Key: "chat_id", Value: chatID},
+		bson.M{"addToSet": bson.M{"users": username}},
+	)
+	return err
+}
diff --git a/main.go b/main.go
index ffa225a..5e1bbc8 100644
--- a/main.go
+++ b/main.go
@@ -80,6 +80,9 @@ func run() {
 
 		text := update.Message.Text
 		chatID := update.Message.Chat.ID
+		username := update.Message.From.UserName
+
+		_ = db.AddUserInChat(chatID, username)
 
 		if strings.Contains(strings.ToLower(text), tag) {
 			_, _ = bot.Send(tgbot.NewMessage(chatID, allUsers))