In World War II, "Leander" served initially in the Pacific and Indian Oceans. Commander Stephen Roskill, in later years the Royal Navy's Official Historian, was posted as the ship's executive officer in 1941. In action on 27 February 1941, she sank the Italian armed merchantman near the Maldives, rescuing 113 of her crew and taking slight damage. On 23 March 1941, "Leander" intercepted and captured the Vichy French merchant "Charles L.D." in the Indian Ocean between Mauritius and Madagascar. On 14 April, "Leander" deployed for support of military operations in Persian Gulf and, on 18 April, joined the aircraft carrier and the light cruiser . On 22 April, "Leander" was released from support duties in the Persian Gulf and took part in search for German raider south of the Maldives.