Wilkinson was commissioned as an ensign in the 43rd (Monmouthshire) Regiment of Foot on 27 December 1842. Promoted to captain in the 42nd Regiment of Foot on 17 October 1851, he was present at the Battle of Alma in September 1854 and the Siege of Sevastopol in Winter 1854 during the Crimean War. He also served at the Siege of Lucknow in Summer 1857 during the Indian Rebellion.