Peel police said officers were called at 3:30 a.m. to a Husky gas station in Brampton near Mississauga Road and Steeles Avenue West.
Investigators said two suspects, both masked and wearing hoodies, told the teller they had a gun.
Police said the teller was not injured.
The two suspects, described as a six-foot-two male with a medium build and a five-foot-eight male with a heavy build, were seen with a white vehicle, investigators added.
Peel police also said they have been made aware of another overnight robbery in Mississauga but did not have details immediately available.
In Toronto, police there said officers were called to a gas station robbery in Etobicoke near Highway 427 and Dundas Street at around 4:26 a.m. on Wednesday.
Toronto police said multiple men entered the gas station, with one person indicating they had a gun as another jumped over the counter and assaulted the employee. Investigators said the suspects took money and lottery tickets.
The employee’s injuries are non-life threatening, police said.
The suspects then fled in vehicle. As of Wednesday morning, police said no arrests have been made.
Police are investigating whether the same suspects are involved in all three robberies.