Toronto-Dominion Bank (TD), Canada's second-largest bank by assets, said it was the victim of a cyber attack on 21 March that took its services temporarily offline for several hours.
The denial-of-service attack occurred mid-morning and prevented its customers from logging on to its website and mobile site.
TD spokeswoman Barbara Timmins said no data was compromised during the attack.
The event follows similar recent attacks on financial institutions in the US and South Korea.