Josh Reddick and Jonny Gomes homered for Oakland, which bounced back from a 3-1 loss in 11 innings in Wednesday's opener.
Oakland starter Bartolo Colon limited Seattle to three hits, including Justin Smoak's solo homer, and struck out six while walking only one in his Oakland debut.
Jason Vargas started for the Mariners and did not factor into the decision, as he was lifted after 6 1/3 innings. The lefty was charged with a run on two hits and two walks with three strikeouts.
Colon, the former Cy Young winner retired the first 13 batters before Jesus Montero singled through the right side of the infield with one out in the fifth.
Miguel Olivo singled with two outs and Michael Saunders drew a walk to give Seattle a mild threat, but Colon induced a ground ball from Brendan Ryan to keep the game scoreless.
Colon did not pitch in the majors in 2010, but returned last season with the New York Yankees and posted a record of 8-10 with a 4.00 earned run average in 29 games, including 26 starts.
Vargas, who was 10-13 with a 4.25 ERA last year, was just as good early. He gave up a one-out single to Cliff Pennington in the first, then did not allow another baserunner until Reddick's two-out double in the fifth.
Seattle finally broke through when Smoak led off the seventh with a home run.
As for local hero and Seattle Mariners superstar Ichiro Suzuki - which is what all of the photographers in the image above are waiting for: after going 4 for 5 in Wednesday's opener, he went oh-fer in four at bats.
Files by Andrew Joseph