The 39-year-old left hander, who retired following a 2010 season in which he went 11-3 with a 3.28 ERA in 21 starts, has signed a one-year, $2.5 million contract with his old club.
Joel Sherman of the NY Post reports that Pettitte and the Yankees had been discussing a comeback "for a while", and that Pettitte expressed his interest to return to the club last night.
Sherman adds that Pettitte will begin workouts with the team immediately and that Opening Day is "in play", but probably not likely.
The 240-game winner and five-time World Series champion will look to add to his borderline Hall of Fame credentials in what will be his fourteenth season as a Yankee.
The addition of Pettitte makes the competition for the already-crowded back of the Yankee rotation more convoluted. The 6' 5" lefty will likely fight for starts with Michael Pineda, Phil Hughes and Freddy Garcia.