In early 1854, shortly after the Crimean War broke out, Campbell accepted the command of the Highland Brigade. He was promoted to brevet brigadier-general on 21 February 1854 and to major-general on 20 June 1854. The Highland Brigade distinguished itself at the Battle of Alma in September 1854 and, with his "thin red line of Highlanders", Campbell repulsed the Russian attack on Balaclava in October 1854. He was promoted to the local rank of lieutenant general on 23 January 1855 and advanced to Knight Grand Cross of the Order of the Bath on 5 July 1855. When the Duke of Cambridge returned to England, Campbell took command of the 1st Division (Guards and Highland brigades) and commanded the Division at the Battle of the Great Redan in September 1855. Promoted to the local rank of full general on 28 December 1855 and the substantive rank of lieutenant general on 4 June 1856, he remained in the Crimea hoping to take overall command, but when General Sir William Codrington was appointed instead, he returned home in a huff. Prince Albert suggested the army in the Crimea be split into two corps d'armee, and Campbell be given one. Lord Panmure requested Queen Victoria ask Campbell return to command one of these corps, and Campbell agreed. However, by the time he had returned, the war was virtually over. He commanded South-Eastern District from July to September 1856. For his services in the Crimean War, he was awarded the Grand Cross of the Sardinian Order of Saints Maurice and Lazarus on 11 August 1856 and the Turkish Order of the Medjidie, 1st Class, on 2 March 1858. The Board of Directors of the East India Company also granted Campbell an annuity of £2,000 per annum for life on 9 June 1858.