Oriji Okwonkwo gave the Impact (2-1-0) the lead in the 14th minute with his first MLS goal. Piatti added another Impact goal a minute later, capitalizing on a defensive miscue as Orlando’s Shane O’Neill misplayed a pass following the kickoff.
Piatti eluded Sacha Kljestan with a cutback and slotted home a right-footed shot to make it 3-0 in the 80th minute.
Dom Dwyer scored with a sliding finish into an open net to pull one back for Orlando City (0-1-2) in the 91st minute.
Montreal’s Zakaria Diallo was shown a red card in the 96th minute after contact with Dwyer.