Tucker Barnhart and Joey Votto also had run-scoring hits as the Reds beat Los Angeles for the second straight night while winning their fourth game in a row.
Max Muncy homered and had two RBIs for the Dodgers, who have lost five of their last six games.
Harvey allowed one hit and struck out two before departing after 55 pitches in his first start since being acquired from the New York Mets for catcher Devin Mesoraco and cash.
The right-hander faced one batter over the minimum, and the lone hit was tainted as right fielder Scott Schebler was unable to locate Cody Bellinger's sky-high fly to right-center field in the second inning. The ball dropped in for a triple between Schebler and center fielder Billy Hamilton.
Harvey responded to the misfortune by striking out Chris Taylor and retiring Muncy on a liner to center.
Gennett has homered in four consecutive games after going deep against right-hander Kenta Maeda (2-3) in the fifth inning. Votto led off the inning with a walk and Gennett followed by depositing a 2-0 slider into the right field seats to give the Reds a 5-0 lead.
Right-hander Austin Brice (1-2) was credited with the victory by the official scorer after striking out four in 1 2/3 innings. He served up the homer to Muncy in the seventh.
Raisel Iglesias entered with two on and one out in the ninth and retired the final two batters for his sixth save.
Maeda allowed five runs and nine hits in 4 2/3 innings. He struck out five and walked two.
Cincinnati gave Harvey a run to work with right at the outset as Jesse Winker doubled on the game's first pitch, moved to third on a wild pitch and scored on Votto's single to center.
Jose Peraza led off the Reds' third with a double and scored on Gennett's one-out single to left field. Barnhart delivered a run-scoring single to right later in the inning to make it 3-0.
The Dodgers were trailing 5-0 when they got on the board in the fifth. Taylor ripped a one-out triple off the fence in center against right-hander Jackson Stephens and scored on Muncy's double that short-hopped the wall in left.
Muncy cut Cincinnati's lead to 5-2 when he sent an 0-2 pitch from Brice over the wall in right with two outs in the seventh.
Eugenio Suarez hit a sacrifice fly in the ninth to give the Reds a four-run cushion.
--Field Level Media
Cincinnati | LA Dodgers | |
Matt Harvey | Player | Kenta Maeda |
No Decision | W/L | Loss |
4.0 | IP | 4.2 |
2 | Strikeouts | 5 |
1 | Hits | 9 |
0.00 | ERA | 9.64 |
Cincinnati | LA Dodgers | |
Scooter Gennett | Player | Max Muncy |
4 | Hits | 2 |
3 | RBI | 2 |
1 | HR | 1 |
7 | TB | 6 |
.800 | Avg | .500 |
Team | Hits | HR | TB | Avg | LOB | K | RBI | BB | SB | Errors |
Cincinnati | 10 | 1 | 16 | .278 | 19 | 7 | 6 | 5 | 1 | 0 |
LA Dodgers | 5 | 1 | 13 | .156 | 12 | 9 | 2 | 1 | 0 | 0 |