Lester was wild from the start, with nine balls in his first 15 pitches, including two walks to load the bases with one out. Up stepped Howie Kendrick, moved from second in the lineup to fifth when Yasiel Puig was scratched, pounced on a post-coaching-mound-visit strike, hitting a double to right field for a quick 2-0 lead.
For Kendrick, it snapped a 12-game skid without an RBI, his first run(s) driven in since June 10.
A triple by Kiké Hernandez and a single by Jimmy Rollins in the second brought home two more runs, and a 4-0 cushion for Carlos Frias to work with.
Frias struggled all day, getting out of a two-on, two-out jam in the first inning, then seeing ground ball double plays help him in both the second and third frames. In the fourth inning, again with two on, pinch hitter Miguel Montero delivered a two-out single, but Chris Coghlan, trying to score from second, was easily thrown out at home on a strong throw by Alex Guerrero in left field.
It was the first career outfield assist for Guerrero. The Dodgers, who have had eight different players start at least six games in the outfield this season, lead the National League with 18 outfield assists.
The fifth inning brought more trouble for Frias, who saw two more get on base, his ninth and 10th baserunners allowed on the day. But Frias rebounded with strikeouts of Matt Szczur and Chris Coghlan to end that threat.
With only 83 pitches, Frias might have continued, but was seen on the SportsNet LA broadcast conferring with trainer Stan Conte in the dugout, seemingly talking about Frias' back or side.
But the bullpen for a second straight day was up to the task, with Joel Peralta, J.P. Howell, Yimi Garcia and Kenley Jansen each tossing a scoreless inning to close out the win.
For Peralta, just off the disabled list on Monday, and Jansen, each pitched a third straight day, just the fourth and fifth Dodgers pitchers to do so this season, joining Garcia (April 22-24), Howell (June 1-3) and Adam Liberatore (June 22-24).
The Dodgers held the Cubs scoreless over the final 13 innings of the series, including 8⅓ innings from the bullpen.
Justin Turner came within a whisker of his sixth home run in his last 10 games with a drive to the left field wall in the seventh inning, but the ball off the top of the basket that was initially ruled a home run was instead a triple. The Dodgers' two triples on Thursday set a season high.
The Dodgers head east and south to Miami, where they will open up a three-game series against the Marlins on Friday night. The first game features a battle of southpaws, with Brett Anderson facing Justin Nicolino.
Home runs: none
WP - Carlos Frias (5-5): 5 IP, 7 hits, 3 walks, 5 strikeouts
LP - Jon Lester (4-6): 4 IP, 4 hits, 4 runs, 4 walks, 5 strikeouts