The Jewish General Hospital says service is returning to normal after a problem in its server room shut down all major computer systems for most of Thursday.
The failure happened at about 7:30 a.m. when the server and computer system room overheated.
The hospital was forced to redirect all ambulances to other health care centres for more than twelve hours. That ban was lifted at about 8 p.m.
Hospital spokesman Glenn Nashen said patient safety had not been compromised.
All scheduled surgeries continued as planned during the day, but some non-urgent services such as elective radiology were cancelled.
In a statement, Nashen said any cancelled appointments will be rescheduled over the next few weekends.
A statement on the hospital's web page apologized for the inconvenience.