Toronto police said they were initially called to the area of Jane Street and Shoreham Drive on Sunday for a break and enter.
When they arrived, officers learned that a man had allegedly assaulted and threatened a woman. He was then arrested at the scene.
During his arrest, officers allegedly recovered a Glock 26 9mm handgun with 18 rounds of ammunition from the man.
Police said Deshawn Walters, 24, was later charged with assault, trespassing, uttering threats, fleeing the lawful custody of a peace officer and 10 other firearm-related offenses, including possession of a prohibited weapon.
Walters is scheduled to appear in court Monday.
Police are asking anyone with information to call 416-808-3100 or Crime Stoppers anonymously at 416-222-TIPS (8477).