Seattle handed the Athletics their fifth straight loss, knocking Oakland below the .500 mark. Texas is the only team with a winning record in the American League West.
Michael Morse and Juston Smoak both drove in a run during the Seattle first and Ibanez boosted the advantage with his long ball in the third.
Hisashi Iwakuma (4-1) fought off the Athletics during a seven-inning stint to get the win. He allowed two runs on four hits and struck out nine.
After Oakland had cut its deficit to three runs heading into the ninth, Tom Wilhelmsen closed out the Athletics with a perfect inning and grabbed his 10th save.
Dan Straily (1-1) took the loss, surrendering six runs on six hits in five innings.