James Fitzgibbon was born in Limerick, Ireland in 1780. He enlisted in the British Army at age 15 as a private soldier. He came to Canada in 1802 by which time he was a sergeant in the 49th Regiment of Foot. In 1806 his commanding officer Isaac Brock made him an officer. This was extremely unusually at the time as most officer's commissions were bought. In 1809 he was promoted to lieutenant.
FitzGibbon fought at the Battle of Stoney Creek in July 1813. Three weeks later he was leading 50 soldiers in guerilla-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 July 22 about an impending sneak attack by 500 American troops. This lead 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 Fencibles.
In 1814 he fought at the Battle of Lundy's Lane. After the war he remained in Upper Canada and became a public servant and a colonel in the militia.
During the Upper Canada Rebellion of 1837 FitzGibbon was appointed Acting Adjutant-General of Militia. He organised and lead the forces that defended Toronto from William Lyon Mackenzie's rebel force.
He was a Freemason.
After his wife Mary died in 1847 he moved to England and in 1850, was appointed a Military Knight of Windsor. He died at Windsor Castle in 1863 and is buried in the crypt of St. George's Chapel.
In 2003 his descendents donated some of his personal effects, including a signet ring and a ceremonial sword, to the Canadian War Museum in Ottawa.