The rookie leftfielder enjoyed a productive spring training with the Marlins and was called up from Class AA Jacksonville earlier in the day.
Yelich singled in the third to tie the game 1-1 after Todd Helton homered to give the Rockies an early 1-0 lead. He then singled in the fifth to put Miami ahead 3-1.
Miami outhit the Rockies 12-5 and won their second consecutive game in the four-game set at Denver. Giancarlo Stanton added an insurance run in the eighth with his 11th home run of the season.
Another Marlins rookie, Jose Fernandez (6-5), notched the win with seven strong innings. Fernandez held the Rockies to two runs on five hits and struck out eight. Steve Chisek picked up his 19th save.
Jhoulys Chacin (9-5) took the loss after allowing three runs on eight hits in seven innings. DJ LeMahieu had two of the Rockies' five hits and scored a run.