At the start of the Crimean War, he was appointed to command the 4th infantry division. The British government gave him a "dormant commission" which meant that if something were to happen to Lord Raglan, Cathcart would take command. At the Battle of the Alma in September 1854, his division saw no action and after the Battle of Balaclava, where his division was called into action, his dormant commission was revoked. He advised a infantry assault on Sevastopol, thinking it could be taken, but was turned down by Lord Raglan.