Manager Kirk Gibson made the announcement Monday. He also says the right-hander is going to be followed in the rotation by righty Trevor Cahill, left-hander Wade Miley and free-agent signee Brandon McCarthy.
Arizona opens the seasons on April 1 at home against the St. Louis Cardinals.
Kennedy was 15-12 with a 4.02 ERA last year after winning 21 games in 2011. He joins Randy Johnson, Curt Schilling and Brandon Webb as the only Diamondbacks to have back-to-back 15-win seasons.
Cahill was 13-12 with a 3.78 ERA last year. Miley finished second to Washington's Bryce Harper for NL Rookie of the Year after winning 16 games last year.