Buchholz (16-7) yielded a lone run on four hits while walking three and fanning six for the Red Sox, who have won four in a row.
"I felt like I had some good life on the fastball and my curveball was better than it has been all season," Buchholz said. "After my last start, I wanted to come out here and throw as many innings as I could and have sort of a bounce back game. That's all I wanted to do."
David Pauley (2-8) pitched well but took the loss after yielding a pair of runs -- one earned -- on six hits with two walks and four strikeouts over six frames for Seattle, which has lost seven straight.
"Everything was working pretty well today. My curveball was working and we stuck with it. I was throwing a lot of strikes and getting a lot of contact," Pauley said of his performance. "It's one of those things, you go up against a guy like Buchholz, he's having a phenomenal year. We fell a little short today but we'll pick it back up."
Seattle had runners at second and third with nobody out and again with two outs in the second but could not score. The complexion of the inning changed when Casey Kotchman was picked off at third for the first out.
Adrian Beltre's home run into the upper deck in left field tied the game in the fourth.
Ryan Rowland-Smith took over for Seattle in the seventh and was greeted by a leadoff single from Scutaro that was followed by Kalish's ground-rule double. Both runners scored when Martinez poked a double just inside the right-field line.
Scutaro walked with two outs in the eighth and scored on a Kalish triple.
Seattle put runners at first and second with one out in the eighth but Hideki Okajima got Branyan to ground into an inning-ending double play.
Boston won five games in a season in Seattle for the first time since 1991. The Sox claimed the season series, 7-3...Buchholz is 9-3 in 14 road starts...Beltre extended his hitting streak to seven games, during which he has 12 hits...Boston has won six of its last eight road contests...Seattle has been held to three runs or less in 17 of its last 18 games...Figgins went 2- for-4 to extend his hit streak to eight games in which he has 16 hits. He has six multi-hit games during the streak...The Mariners are 33-33 when scoring first.