The pair traded insults late last night, after the 30-year-old had criticised Newcastle, but the Englishman has now taken to the social networking website to issue an apology
The pair, who spent the 2006-07 season together at the Etihad Stadium, got into an angry back-and-forth after Barton tweeted a rumour that Marseille team-mate Loic Remy was set to choose a move to QPR instead of Newcastle.
Hamann took exception to this, and the pair spent time trading insults on the social networking website, before Barton took to his account this morning to apologise.
He tweeted: “I've slept on it. I have no right to question a man I hardly know. I must, therefore apologise for my part in last night's heated exchange.”
The pair mentioned details about their time as team-mates and were engaged in the row for just over an hour.