He succeeded to the title Lord Kinsale in 1669 and was educated at Oxford under Dean of Christ Church and Bishop of Oxford, Doctor John Fell. A letter written by Dr. Fell in 1678 complains that de Courcy is "addicted to the tennis court, proof against all Latin assaults and prone to kicking, beating and domineering over his sisters; ... fortified in the conceit that a title of honour was support enough, without the pedantry and trouble of book-learning."
He served as a captain in a Troop of Horse for King James II, later becoming a Lt. Colonel in the regiment of Patrick Sarsfield. He derived an income from a pension awarded to the 22nd Lord by King Charles II
He sat as a peer in the 1689 Parliament in Dublin, was attained in 1691 and enjoyed the reversal of attainder in 1692. Dying without issue, he was succeeded by his cousin, Gerald de Courcy.