The White Sox have lost seven straight games, their longest slide since dropping seven in a row in September 2011.
Tom Wilhelmsen, who had blown three of his last four save opportunities, gave up a two-out RBI single to Adam Dunn in the ninth but earned his 13th save.
Saunders (4-5) returned to his winning ways at Safeco Field, allowing one run and five hits in 6 1-3 innings with one walk and five strikeouts. Saunders is 10-1 at the Mariners' ballpark. The lone loss came in his previous home start against Texas on May 24, when he gave up eight runs in five innings.
Chicago won its previous eight games in Seattle, but even the formerly friendly venue and a starting pitcher with a history of success against the Mariners couldn't stop the losing streak.
John Danks (0-2) allowed four runs three earned and seven hits in six innings, striking out five and walking one in his third start of the year. The loss snapped Danks' seven-game winning streak against the Mariners in his last eight starts against Seattle, he was 7-0 with a 1.31 ERA.
The Mariners took the lead for good in the third inning. With one out, Kyle Seager beat out a bunt single and Kendrys Morales drove him home with a double off the center-field wall. Ibanez capped the inning with his 10th home run.
Ibanez fell behind 0-2 but kept fouling off pitches, working the count full and homering to right field on the 13th pitch to give the Mariners a 4-1 lead.
Chicago opened the scoring in the second. Dayan Viciedo hit a bloop double to center and scored on Jeff Keppinger's single.
Seattle answered in the bottom half when Jesus Sucre's RBI single tied it at 1.
NOTES: White Sox bench coach Mark Parent was ejected by plate umpire Dale Scott in the seventh. ... The Mariners held a short, closed-door team meeting before taking batting practice. "I just wanted to talk about where we're at," manager Eric Wedge said. "We've had a lot of tough losses these first couple months, more so than I've seen, and I'm proud of the way they've handled it." ... Seattle OF Franklin Gutierrez (right hamstring strain) ended his rehab assignment with Triple-A Tacoma, but remains on the disabled list. Mariners head athletic trainer Rick Griffin said Gutierrez still has lingering hamstring issues, and the Mariners plan to put him on another rehab assignment. ... The White Sox activated infielder Gordon Beckham from the 15-day disabled list and designated infielder Tyler Greene for assignment.