Born the son of Gerald Valerian Wellesley (brother of the Arthur Wellesley, 1st Duke of Wellington) and Lady Emily Mary (daughter of Charles Cadogan, 1st Earl Cadogan), Wellesley joined the Royal Navy in 1828.[1] After initial training at the Royal Navy College at Portsmouth and promotion to lieutenant on 22 April 1838, he was posted to the first-rate HMS Princess Charlotte in the Mediterranean Fleet.[2] He transferred to the fifth-rate HMS Castor in March 1839 and took part in operations on the coast of Syria taking part in the capture of Acre in November 1840 during the Oriental Crisis.[1] He joined the fifth-rate HMS Thalia on the East Indies Station in November 1841 and, having been promoted to commander on 16 April 1842, he transferred to the brig HMS Childers also on the East Indies Station.[2]