Const. Daniel Lacoursière says the incident happened on Saint-Urbain Street near Saint-Joseph Boulevard West just after 3 a.m.
The man had two clients in his cab when one of them assaulted him with a sharp object.
While being assaulted, the taxi driver lost control of the car and hit two parked cars.
"After the impact the two suspects fled the scene," Lacoursière said.
Police are looking for a white male in his 50s and a white female in her 40s.
It is not clear why the passengers attacked the driver.
The driver is in the hospital with minor injuries.