Los Angeles erased a four-run deficit and still endured its sixth loss in a row when J.T. Realmuto's tiebreaking homer in the sixth inning helped Miami win 6-5.
''It's the same story: We just didn't get it done,'' Dodgers manager Dave Roberts said.
Miami clinched the series after another last-place team, Cincinnati, swept a four-game set at Los Angeles last week. The Dodgers and the rebuilding Marlins have identical 16-26 records.
''I think everyone would be surprised,'' Marlins manager Don Mattingly said.
Justin Bour hit a two-run homer for Miami , his ninth. Starlin Castro tied a career high with four hits to hike his batting average to .300.
Yasmani Grandal hit his seventh home run and singled in a run for the Dodgers, who fell to 4-14 in games decided by one or two runs.
The Marlins' Elieser Hernandez, a Rule 5 draft pick making his first career start, allowed one run in five innings and left with a 5-1 lead.
Los Angeles quickly erased it, scoring four runs in the sixth against Miami's bullpen. Max Muncy's two-run double off Drew Steckenrider made it 5-all.
Steckenrider (2-1) regrouped to retire five batters. Brad Ziegler pitched around a leadoff single in the ninth for his seventh save, with Justin Turner bouncing into a game-ending double play.
The Dodgers' bullpen has struggled all season, and Pedro Baez (1-2) gave up the sixth-inning homer by Realmuto.
''It's disappointing,'' Baez said through a translator. ''You see the team start to get a rhythm going, and then to not be able to contribute - it's frustrating.''
Los Angeles rookie Walker Buehler gave up a season-high five runs, four earned, in five innings. That included Bour's opposite-field homer in the fifth.
''I gave up too many runs for us to win,'' Buehler said. ''The ball Bour hit, I don't know if there's another human who can hit that ball out of the ballpark. Just a gigantic, really strong human.''
Brian Anderson's two-out RBI single in the first put Miami ahead. An error by Dodgers shortstop Chris Taylor led to an unearned run in the third, which scored on Castro's single.
The Dodgers' Yasiel Puig went 0 for 4 and stranded five runners, including two in the eighth.
''It's on all of us,'' Roberts said. ''For quite some time, to be quite honest, we haven't been synched up.''
HE LOVES LA
Realmuto has at least one hit in all 21 career games against the Dodgers.
''You know you've hit them good, and they know you've hit them good,'' Mattingly said. ''I think there's a little psychological factor.''
Hernandez was inserted into the rotation, and LHP Caleb Smith's start was pushed back a day. LHP Jarlin Garcia, who has started six games, was available in the bullpen but will rejoin the Miami rotation at some point, Mattingly said.
Dodgers: LHP Rich Hill (blister) threw a bullpen and is on track to start Saturday at Washington. ... LHP Tony Cingrani (left shoulder inflammation) is expected to be activated from the disabled list Saturday.
RHP Kenta Maeda (2-3, 4.75 ERA) is scheduled to start for the Dodgers in the series finale Thursday afternoon against Smith (2-4, 3.63).
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