On the outbreak of the South African War in October 1899 Bell enlisted as a private in the 1st West Australian (Mounted Infantry) Contingent. He first saw action at Slingersfontein, and later took part in the relief of Johannesburg and of Pretoria and the battles of Diamond Hill and Wittebergen; on 19 July 1900, in a sharp engagement at Palmeitfontein, he was seriously wounded and was invalided to England. He returned to Perth in February 1901, was commissioned lieutenant in the 6th Contingent on 8 March, and re-embarked for South Africa. On 16 May at Brakpan, Transvaal, while his unit was retreating under heavy fire, he went back for a dismounted man and took him up on his horse. The animal fell under the extra weight and Bell, after insisting that his companion take the horse, covered his retreat; for this action he received the Victoria Cross—the first awarded to a Western Australian.