Parker joined the army in the 1st Foot Guards and was lieutenant and captain in 1749 and captain and lieutenant-colonel in 1755. He became Colonel in 1762 and Major-general in 1770. From 1773 to 1782 he was Colonel of the 20th Foot. He became a Lieutenant-General in 1777 and was Colonel of the 12th Dragoons from 1782.
Parker married Jane Lady Dormer, widow of Sir Charles Cottrell-Dormer and daughter of Charles Adelmare Caesar in May 1782. He died on 6 September 1791.