At the age of eighteen, newly promoted to lieutenant on 22 October 1899, White saw service with his regiment in the Second Boer War in South Africa. He was employed under the Military Governor of the Orange River Colony, and took part in the advance to relieve the Siege of Kimberley, including the Battle of Magersfontein (11 December 1899). After the British troops had finally lifted the siege and entered Kimberley in February 1900, he took part in the Battle of Paardeberg (February 1900); and operations in the Orange Free State from March to May 1900, including the battles of Poplar Grove, Driefontein, Vet River and Zand River (March 1900). From May 1900 he served in the Transvaal, where he took part in the occupation of Johannesburg and Pretoria. He also took part in the battles of Belfast and Lydenburg (August 1900). For his war service, he was mentioned in despatches, received the Queen's South Africa Medal with five clasps, and was decorated with the Distinguished Service Order (DSO). "The London Gazette" of 2 July 1901 in its DSO citation reported:James Robert White, Lieutenant, The Gordon Highlanders. For having, when taken prisoner, owing to mistaking advancing Boers for British troops, and stripped, escaped from custody and run six miles, warning Colonel de Lisle, and advancing with him to the relief of Major Sladen's force.