Fitzwilliam was born of Irish parents near Holborn in London on 8 Aug. 1788, In 1806 he was actor and property man with Trotter, manager of the theatres at Southend and Hythe.

Under the management of Thomas Dibdin he rose at this house to the height of his popularity, his best parts being Leporello, Dumbiedykes in the Heart of Midlothian, Patch, Partridge in Tom Jones, and Humphry Clinker.

Fitzwilliam – who had once appeared at Drury Lane for the benefit of T. P. Cooke, playing Sancho in Lovers' Quarrels and singing a song, "Paddy Carey", in which he was very popular – joined the regular company at that house 10 November 1821 as O'Rourke O'Daisy in Hit of Miss.

Padreen Gar in Giovanni in Ireland, Loney Mactwolter in the Review, and other Irish parts were assigned him.

About 1845 he retired on an annuity from the Drury Lane Theatrical Fund, and died at his house in Regent Street 30 March 1852.