On July 15, 2005, Leiter was acquired by the New York Yankees, who had four starting pitchers on the disabled list, for a player to be named later. His first start as a Yankee since April 26, 1989, came on July 17, 2005, against the division-leading Boston Red Sox. Leiter won the game, pitching 6 innings, allowing one run and three hits, and striking out eight. After several starts with mixed success, he informed Joe Torre that he would be willing to pitch out of the bullpen, where he would stay for the latter part of the season, yielding his starting slot to Aaron Small.