Long available in other social networks, the new service is part of an update of the Twitter app for iOS and Android that is now available.
Users can tag up to 10 friends in a picture and still have 140 characters to write a tweet, says the company.
Anyone who doesn't want to be tagged can remove the label later or even block tags entirely.
The update also allows users to include up to four pictures with a tweet. Previously, the limit had been one photo.