Ethier gave the Dodgers a 3-0 lead in the second, driving a 1-1 pitch from Jason Vargas to center field after Casey Blake led off with a double and James Loney singled.
He made it 7-2 in the sixth with a drive into the right-field pavilion off Vargas (3-3). He capped his big night with a leadoff shot in the eighth off Miguel Batista for his 14th homer.
It was Ethier's fifth career multihomer game.
Clayton Kershaw (5-5) allowed two runs and five hits over six innings and struck out eight, helping the defending NL West champions improve baseball's best record to 48-26. The 21-year-old left-hander hasn't given up more than five hits in any of his last 11 starts, but is only 5-3 during that stretch despite a 2.48 ERA in those eight outings.
Seattle's Ichiro Suzuki had his sixth straight multihit game giving him a major league-leading 34 this season. The two-time AL batting champ played his first game at Dodger Stadium since March 23, when his two-run single in the 10th inning helped Japan capture its second straight World Baseball Classic championship.
Vargas (3-3) gave up five runs and nine hits over 4 2-3 innings. The left-hander made one other start against Los Angeles, winning 7-1 on Aug. 21, 2005, with a six-hitter for his only complete game in 29 big-league starts.
Seattle second baseman Jose Lopez, in his second game back after missing the previous six while on the bereavement list, had two run-scoring singles. He leads the Mariners with 44 RBIs.
Kershaw was perfect the first time through the Mariners' lineup. But Suzuki led off the fourth with a single and scored from second on a single by Lopez. The Dodgers got the run back in the bottom half when Blake led off with his 11th homer.
In the fifth, Matt Kemp legged out his fifth triple of the season and Kershaw singled Kemp home for his first RBI in 51 career at-bats.Ken Griffey Jr., fifth on the career home run list with 619 and one shy of Jim Thome's interleague-record 55 homers, did not play because the DH rule is not in effect in NL ballparks. Griffey has started only eight games in the outfield this season, and was the DH in 42 others.
