The Dodgers have downed the Reds in 14 of their last 17 meetings.
Kershaw (7-3) lasted 7 1/3 innings, giving up seven hits and a run. He has a 6-1 record since the first week of May.
James Loney put the Dodgers in front with a two-run double in the fifth and Ethier hit his homer in the sixth, his 12th of the season.
Manny Ramirez contributed his second homer in as many games in the ninth.
Mike Leake (5-1) gave up nine hits and five runs over six innings in the first loss of his career.