The Dodgers remained 2 1/2 games behind NL West-leading San Francisco.
Betts drove in four of the Dodgers' five runs. He had a sacrifice fly in the third that made it 2-0.
Buehler (14-3) allowed two runs and six hits in seven innings. The right-hander struck out five and walked two.
“Tonight probably wasn’t my best,” said Buehler, whose 2.31 ERA is three points behind NL leader and teammate Max Scherzer. “Kind of forget about it now.”
Buehler drew a key walk from Chris Paddock that set up Betts, who blasted his 20th homer on the first pitch from Craig Stammen.
Paddock (7-7) got the first two outs of the fifth and then Gavin Lux singled. He walked Buehler on four pitches before getting pulled, having thrown 30 more pitches than Buehler at that point.
“Still kind of fighting getting back into the groove after that long month off,” said Paddock, making his third start since coming off the injured list with a left oblique strain. “Last start the velo was down as well against the Astros. Just kind of going though a little dead arm.”
Paddock gave up four runs and three hits in 4 2/3 innings. The right-hander struck out four and walked two.
Kenley Jansen retired the side in the ninth for his 32nd save.
Betts was solid defensively, too. He made a shoe-top catch of a sinking liner from Trent Grisham with a runner on second to end the seventh.
The Padres closed to 5-4 in the eighth on back-to-back RBI singles by former Dodger Manny Machado and Tatis off Blake Treinen. Joe Kelly came in and struck out Wil Myers and Tommy Pham on a combined seven pitches to strand Tatis at third.
“When Joe Kelly is healthy, he’s pretty electric and he showed that,” Buehler said.
Machado had three hits, scored two runs and drove in another.
“The way Manny and Tatis swung the bats for us, that was encouraging,” Padres manager Jayce Tingler said. “Got to hope that some of that becomes contagious up and down the order.”
Dodgers: INF-OF Chris Taylor had the night off. He's been dealing with an unspecified neck injury, although it's not believed bad enough to land him on the IL. He aggravated it on Friday after making a catch at the wall. “This neck thing has really checked him up,” Roberts said.
Tatis returned to his natural position of shortstop and went 3 for 4 as a result of All-Star Jake Cronenworth getting hurt Friday. Cronenworth sustained a small fracture on his left ring finger after getting hit by a pitch. Tatis initially moved away from shortstop to protect his left shoulder, which has been partially dislocated multiple times this year. But playing him in the outfield, where he moved last month, meant the Padres had to sit one of three outfielders — Myers, Pham and Grisham — every day. And San Diego is in desperate need of offense as the team makes a push for the second NL wild card.
Machado's six homers at Dodger Stadium are the most by a Padre in a single season, passing Nate Colbert, who had five in 1971.
Padres: LHP Blake Snell (7-6, 4.22 ERA) has turned around an inconsistent season with a great run since the beginning of August.
Dodgers: RHP Max Scherzer (13-4, 2.28) is 9-0 with a 2.23 ERA in his last 15 starts since June 4.
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