The robbery happened at about 7:15 a.m. at 11730 Yonge Street in Richmond Hill, just as employees had arrived to open up the bank.
Police say the suspect was armed with a silver handgun and took an undisclosed amount of cash.
He then fled in a bank employee's vehicle, a black Santa Fe. The vehicle was recovered by police at 205 Tower Hill Road.
The suspect is described as white male, 5'7'', wearing a black hoodie and jeans. Police say he also wore a camouflage-patterned balaclava and a black backpack.
Anyone with information is asked to contact investigators at 1-866-876-5423, ext. 6630, or Crime Stoppers at 1-800-222-8477.