Suliman Mohamed, 21, faces charges of participating in the activities of a terrorist group, and conspiring to participate in terrorism with 24-year-old twin brothers who were arrested on Friday.
Royal Canadian Mounted Police Chief Superintendent Jennifer Strachan yesterday said the arrests underscore that there are Canadians "who have become radicalised to a violent ideology, and who are willing to act upon it."
Strachan in a statement linked the latest arrest with the arrests on Friday of Ashton Carleton Larmond and Carlos Larmond.
The arrests come after Islamist attacks in France killed 17 people, including 12 people at the satirical magazine Charlie Hebdo.
In October, two soldiers were killed in separate attacks in Canada. In one, a soldier was fatally shot while standing watch at the War Memorial in Ottawa. His attacker, Michael Zehaf-Bibeau, then stormed into parliament and exchanged fire with police before being shot dead.