on february 8, 2008, bédard was traded to the seattle mariners in a 5-for-1 deal sending outfielder adam jones and pitchers george sherrill, tony butler, chris tillman and kam mickolio to the orioles. on february 13, mariners manager john mclaren announced that he would be their opening day starter. bédard then signed a one-year, 7-million dollar deal with the mariners on february 15, avoiding salary arbitration. he was 6–4 with a 3.67 era in 15 starts for the mariners in 2008 but on july 10, 2008, he was placed on the 15-day disabled list with stiffness in his left shoulder. he missed the rest of the season and underwent arthroscopic surgery on the shoulder on september 26.