FitzGibbon fought at the Battle of Stoney Creek on 6 June 1813. Three weeks later, he led 50 soldiers in guerrilla-style raids on a large American force that had captured Fort George on the Niagara Peninsula. It was he who was warned by Laura Secord on 22 June about an impending surprise attack by 500 American troops. This led to the Battle of Beaver Dams near present-day Thorold, Ontario, where FitzGibbon's force, together with about 400 Mohawk and Odawa warriors, defeated the Americans and took 462 prisoners. The victory made FitzGibbon a popular hero and he was promoted to Captain in the Glengarry Light Infantry Fencibles. In 1814 he fought at the Battle of Lundy's Lane.