Ottavino (3-1) took over in the fifth inning for a tiring Drew Pomeranz.
Carlos Gonzalez had a sacrifice fly in the first inning and rookie Jordan Pacheco added an RBI single in the third for the Rockies, who prevented the Dodgers from overtaking NL West-leading San Francisco following the Giants' loss at St. Louis.
Rockies manager Jim Tracy was ejected by third base umpire and crew chief Mike Everitt in the bottom of the seventh when he slammed his cap to the ground following the reversal of a call on a sinking liner by Shane Victorino first ruled an out. TV replays showed center fielder Dexter Fowler trapped the ball.
The Dodgers had a runner at second with two outs when first base umpire Mike Estabrook made the out call on Fowler's sliding catch attempt. The umpires eventually huddled after Dodgers manager Don Mattingly came out to argue the initial ruling.
Tracy remained on the field for several minutes in an animated discussion with Everitt after he got tossed. The Dodgers failed to capitalize after play resumed because Ottavino retired Mark Ellis on a flyball to left with runners at the corners.
Ottavino also got his first big league win at the Dodgers' expense, on June 1 at Coors Field.
Matt Belisle, who came in having allowed 18 earned runs over 19 2-3 innings in his 17 previous appearances at Dodger Stadium, escaped his own jam in the eighth by striking out Luis Cruz with two men on. Rafael Betancourt pitched a perfect ninth for his 18th save in 22 chances.
Dodgers lefty Chris Capuano (10-8) allowed two runs and nine hits in seven innings and struck out seven.
Pomeranz threw 84 pitches over four innings, allowing three hits and three walks while striking out seven. In his previous four starts, he was 0-3 with a 9.35 ERA after pitching 6 1-3 innings of one-hit ball in a 5-1 victory at Washington on July 6
Pomeranz gave up singles to his first two batters, but escaped his jam by striking out Juan Rivera with two men in scoring position. Two innings later, he walked his first two batters before retiring Matt Kemp on a double-play grounder and striking out Hanley Ramirez with Victorino at third base.
The Rockies, who have played without shortstop Troy Tulowitzki for the last 58 games because of a groin strain, announced Monday that the other remaining star of their 2007 pennant-winning infield - first baseman Todd Helton - will undergo arthroscopic surgery Friday to repair a torn labrum in his right hip.
Helton, a five-time All-Star and three-time Gold Glove winner who is the franchise leader in almost every major offensive category, turns 39 on Aug. 20 and is determined to return for the final season of the two-year, $9.9 million contract extension he signed in March 2010.
Capuano gave up singles to two of his first three batters before Gonzalez hit a sacrifice fly for his team-high 74th RBI. In the third, Capuano gave up three straight one-out singles - including a run-scoring hit by Pacheco - but minimized the damage by retiring Ramon Hernandez on a double-play grounder after an intentional walk to Gonzalez.
NOTES: Rockies 2B Chris Nelson, who missed 17 games because of an irregular heartbeat, was reinstated from the disabled list to replace Helton on the active roster. ... The Dodgers designated OF Tony Gwynn Jr. for assignment and recalled OF Jerry Sands from Triple-A Albuquerque. ... The Dodgers named Janet Marie Smith as Senior VP of Planning and Development, the same job she had with the Atlanta Braves, Boston Red Sox and Baltimore Orioles. She will oversee upgrades and enhancements to Dodger Stadium, which opened in 1962. ... Tracy said that Pacheco, Matt McBride and Tyler Colvin all will get playing time at 1B in Helton's absence - along with Michael Cuddyer when he gets off the disabled list. Pacheco started there on Monday night.