Dan Haren (3-0) was charged with five runs - two earned - and seven hits over 7 1-3 innings. The right-hander struck out five in his fourth start of the season, six days after his 8-6 victory over the Diamondbacks at Phoenix.
Haren departed with an 8-4 lead and was replaced by Brian Wilson, who gave up a two-run double by Martin Prado before retiring Chris Owings on a grounder with runners at the corners to end the eighth. Kenley Jansen pitched a scoreless ninth for his sixth save.
Mike Bolsinger (0-1) made his first major league start and was charged with seven runs - six earned- and seven hits in four-plus innings. He struck out five of the first 11 batters he faced.
The 26-year-old righty was inserted into the rotation after Trevor Cahill, who went 0-4 with a 9.17 ERA before earning his first career save on Friday.
Bolsinger pitched three innings last Monday in his big league debut, allowing two runs and six hits against the New York Mets after winning both of his starts with Triple-A Reno.
Los Angeles was trailing 4-0 in the fourth when Ethier hit his second homer of the season.
The Dodgers grabbed an 8-4 lead with five more in the fifth, including a two-run single by Adrian Gonzalez and a two-run double by Matt Kemp. Haren led off the inning with a single and later scored when Prado fielded a potential double-play grounder to third base by Hanley Ramirez with the bases loaded and dropped the ball as he looked toward second base.
Bolsinger got his first big league hit during Arizona's four-run third. Paul Goldschmidt hit a two-run single with the bases loaded. Ramirez's fifth error of the season at shortstop made three of the runs unearned.
NOTES: Dodgers ace Clayton Kershaw, who hasn't pitched in a game since beating the Diamondbacks in the season opener in Australia, is scheduled to throw to batters in simulated game conditions on Sunday. The reigning NL Cy Young Award winner has been sidelined by a muscle strain in his upper back. ... Haren, who came in leading all active major leaguers with a 4.09 strikout-to-walk ratio, has 20 strikeouts and two walks this season. ... The Dodgers' rotating outfield of Ethier, Kemp, Carl Crawford and Yasiel Puig all entered Saturday hitting .235 or lower through the team's first 17 games. ... Gonzalez extended his hitting streak to 14 games. His longest streak in the majors is 18, two seasons ago with Boston.