On 2 April 1801, Warden was promoted to ship surgeon on his new ship, the frigate HMS Alcmene, during the Battle of Copenhagen. On 10 August 1805, Warden was the ship surgeon on the frigate HMS Phoenix when it engaged the French frigate Didon off Cape Finisterre. Severely wounded in the battle, Warden was later evacuated to Greenwich Hospital in England for recuperation.