He assumed by Royal licence the additional surname of Ormsby the same year.
He joined the British Army and served as a lieutenant in the 1st Dragoon Guards in 1800, was promoted to captain in 1802, to major in 1802 and to brevet major in 1813.
Ormsby-Gore was elected to the House of Commons for County Leitrim in 1806, a seat he held until 1807, and then represented Caernarvon from 1830 to 1831 and North Shropshire from 1835 to 1857.
His eldest son John Ormsby Gore was M.P.
His second son William became 2nd Baron Harlech after the death of his brother.