Following the outbreak of the Second Boer War in late 1899, his battalion was sent to South Africa, where he served as adjutant of the battalion throughout the war. He was present at the battles of Colenso (15 December 1899), Vaal Krantz (5–7 February 1900), Tugela Heights and Pieter's Hill (14–27 February 1900) and the Relief of Ladysmith (1 March 1900), and later in operations in the Transvaal and Orange River Colony. For his services in the war, he was twice mentioned in despatches, received the Queen's South Africa Medal and was appointed a Companion of the Distinguished Service Order (DSO). After peace was declared in May 1902, Bols left South Africa on board the SS "Bavarian" and arrived in the United Kingdom the following month.