The Dodgers had back-to-back four-run innings to take control, but San Diego trailed only 8-6 heading into the ninth and tied the score on a two-run homer by Chase Headley.
Andrew Cashner was then called on by the Padres to get the game into extra innings, but after retiring the first two batters in the bottom of the ninth he walked Mark Ellis, Matt Kemp and James Loney.
Cashner (0-1) then walked Ethier on four pitches to force in the winning run. Los Angeles won for the seventh time in eight games this season and has the best record in baseball.
Ellis and Ethier both drove in two runs in the third inning and Los Angeles produced four more in the fourth -- the last two coming on a homer from Kemp.
The win went to Kenley Jansen (2-0), even though he gave up the homer to Headley in the top of the ninth.