Yoenis Cespedes, Stephen Drew and Coco Crisp added an RBI apiece for the Athletics, who maintained their lead atop the AL wild card standings.
Anderson (4-0) gave up one unearned run on six hits while striking out four for Oakland, which has won two in a row since a three-game skid.
"His performance, I think, has been more than we could ever expect," Oakland manager Bob Melvin said. "He fought himself a little at times tonight. His stuff always plays."
Trayvon Robinson knocked in the lone run for the Mariners, who have lost three of four.
Hisashi Iwakuma (6-4) allowed five runs -- four earned -- on six hits over 3 2/3 innings. He struck out three and walked two.
"We're just not getting the production we need; we're just not finishing things off and that's been one of our biggest issues this year offensively, just finishing innings off and taking advantage of opportunities," Seattle manager Eric Wedge said.
The A's got on the board in the first inning. Josh Reddick reached base when he grounded into a fielder's choice. Yoenis Cespedes followed with a sharp line drive down the left-field line, scoring Reddick. Third baseman Kyle Seager was charged with an error on the play.
Seattle tied the game in the second. Michael Saunders hit a ground-rule doubled to center field and Miguel Olivo reached first on shortstop Drew's fielding error. A run scored when Robinson reached on a fielder's choice.
But Oakland scored four runs in the fourth to create some distance. Cespedes doubled, stole third and raced home on Drew's single to right. Kottaras homered to right two batters later. Cliff Pennington singled and scored on Crisp's double to make it 5-1.
Cespedes' sacrifice fly in the ninth accounted for the final margin.
Oakland leads the season series by an 8-7 margin ... Seattle went 0-for-7 with runners in scoring position and stranded nine ... The A's had 10 hits, compared to seven for the Mariners ... The Athletics extended their road winning streak to eight games, longest since winning eight straight July 19- Aug. 7, 2005.
09/09 01:42:07 ET