Eric Chavez hit a two-run homer and Curtis Granderson had a two-run single off Kevin Millwood, sending the AL East leaders to their second consecutive win following a 3-9 slide.
Sabathia (11-3) rebounded from a rocky start against Boston with another overpowering performance against his favorite foe. Pitching in the sort of thick humidity that he's always enjoyed, the big lefty improved to 8-0 with a 1.20 ERA in his past eight starts against the Mariners.
Going into the ninth, Sabathia had given up only Casper Wells' solo homer with one out in the fourth and Miguel Olivo's eighth-inning double. He walked Brendan Ryan to start the inning before Dustin Ackley drove his eighth homer deep into the seats in right.
Yankees manager Joe Girardi came out for a quick chat with Sabathia, who retired the next three batters as the crowd of 45,872 chanted "CC! CC!" Sabathia threw 72 of 103 pitches for strikes in his 35th career complete game and second this season.
Dating to May 2006, Sabathia has yielded no more than one earned run in nine of 11 starts against Seattle. The last time he faced the Mariners, he whiffed a career-high 14 on July 26 last season.
Sabathia is 12-4 in 20 career starts against the Mariners, who are managed by his former skipper in Cleveland, Eric Wedge. Russell Martin was behind the plate after backup Chris Stewart caught Sabathia's previous 16 starts.
Ichiro Suzuki started a rally against his former team and the Yankees helped Sabathia improve to 4-0 in his last seven outings.
Last in the AL West, the Mariners had won 13 of 17 and were trying for their first eight-game winning streak in five years. They began a nine-game trip that also takes them to Baltimore and Los Angeles.
Still speedy at age 38, Suzuki opened the third inning by beating out a dribbler that was picked up by an off-balance Millwood (4-9) between the mound and third base. Martin doubled to left-center on an 0-2 pitch and both runners scored when Granderson singled to center on Millwood's next delivery.
The 37-year-old right-hander held it there, however, and was one out from getting through the sixth inning unscathed when Chavez hit a high fly ball to right. The ball fell just beyond the glove of a leaping Eric Thames and hit the cement ledge right behind the fence, maybe 320 feet from home plate.
Chavez, who was using teammate Andruw Jones' bat, became the ninth Yankees player with at least 10 homers this season - one shy of the club record set in 1998.
Robinson Cano and Raul Ibanez both added an RBI single in the seventh against the Seattle bullpen. Carter Capps faced three hitters in his major league debut, retiring only Derek Jeter on a sacrifice bunt.
NOTES: Yankees 1B Mark Teixeira went 1-for-4 with a single in his return to the lineup after missing two games with a sore left wrist. ... Mariners ace Felix Hernandez (9-5, 2.79 ERA) pitches Saturday against RHP Hiroki Kuroda (10-7, 3.28). Hernandez is 5-0 with a 1.60 ERA in his last nine starts. ... Seattle OF Michael Saunders was rested with some stiffness in his legs, Wedge said. Saunders is 1-for-11 with five strikeouts against Sabathia. ... Mariners reliever Charlie Furbush was scheduled to throw an inning during a rehab assignment with Triple-A Tacoma. The left-hander has been on the DL since July 18 with a strained triceps. ... In the fourth inning, the barrel of Dustin Ackley's broken bat sailed into the stands and struck a woman sitting about seven rows behind the New York dugout. She was immediately tended to by medical workers, and the Yankees tossed out towels to help. Fans clapped as the woman walked up the aisle under her own power, holding what appeared to be a white cloth to her head.