The 31-year-old Brazilian joined the Premier League side in 2012 after a six-year spell with Inter but fell out of favour last season, featuring in just 13 games across all competitions.
Despite the arrival of new boss Manuel Pellegrini ahead of the new campaign, the defender's chances at the Etihad Stadium appeared limited and he was left out of the club's pre-season squad that is currently touring South Africa.
He has now made his return to Serie A, with a statement on City's website confirming: "Maicon has joined AS Roma on a permanent deal. Everyone at Manchester City wishes Maicon good luck at his new club."
Maicon will hope to find a return to first-team football under new Roma boss Rudi Garcia.
He made over 200 appearances during his spell with Inter from 2006 to 2012, establishing himself as the club's first-choice right-back.
He has also represented his country over 50 times since making his debut in 2003, and was a part of their 2004 Copa America and 2005 Confederations Cup triumphs.
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