Pettitte, 39, will be added to the team's active roster following a minor-league comeback attempt and will pitch Sunday against Seattle, the GM said.
The veteran hurler, who played with the Yankees from 1995-2003 and again from 2007-10, retired after last appearing in Game 3 of the 2010 American League Championship Series.
He changed his mind this season and returned to the team in spring training on a minor league contract.
The 240-game-winner posted a 3.71 earned run average in four minor-league appearances.
Easer Egg Roll brings thousands to White House
Moore to attend retreat in to avoid Kutcher's wedding