Public health officials at a news conference on Saturday would not confirm whether the new case is a child or an adult, nor whether it is linked to Quebec's previous 18 cases.
The source of the outbreak for the first 18 cases has been traced to Disneyland, California.
All of the Quebec cases have been concentrated in the Lanaudiere region, northeast of Montreal.
None of the people infected in Quebec were vaccinated for the disease.
Quebec health authorities said that several dozen other people are currently under observation, since measles has a two-week incubation period.
While measles was declared eliminated from the U.S. in 2000, the illness has reappeared in recent years.
Toronto Public Health reported a new confirmed case on Saturday bringing the total number in Ontario to 18.
Manitoba has also reported a case.