Fitzgerald was returned to the Irish parliament for Kildare borough by his eldest brother in 1783 and for Dublin city, as Grattan’s colleague, in 1790. He followed the tradition of his family in opposing administration.
In 1807 he came in for county Kildare on the family interest, as an opponent of administration, though expected to be a ‘feeble’ one,
In 1814 he vacated his seat to make way for his nephew Lord William. He retired to Boyle Farm where he was ‘surrounded by an affectionate family and numerous friends, who were sure to find under his roof the most cordial reception, and all that was hospitable and convivial’.
