Monckton returned from the Caribbean later in 1762. He was subsequently named Governor of the Province of New York. He held this position until 1765, even though he left North America for good in 1763 to return to England. In 1765 Monckton was appointed governor of Berwick-upon-Tweed. In 1770 he was promoted to the rank of lieutenant-general. Later, Monckton became interested in becoming the British military commander of India and although he had the East India Company nomination and some royal support, he was not offered the position. Instead, he was offered the command of the British army in North America which he declined. In 1778 he became governor of Portsmouth and MP for the town in the Admiralty interest. Also that year, his younger brother, Henry Monckton was killed while leading the grenadiers at the Battle of Monmouth in New Jersey during the evacuation of Philadelphia. The following year, Robert Monckton organised Portsmouth's defences against the Armada of 1779 (during the American War of Independence). Monckton died on 21 May 1782 at age 55 and is buried in St. Mary Abbot's Church, Kensington, London.