Mitchell returned to South Africa in the Queen's Own Yorkshire Dragoons, where he fought in the Second Boer War, which saw him miss the entire 1900 English cricket season.

In 1901 he was back playing for Yorkshire, making seven centuries in a season that earned him the accolade as one of the Wisden Cricketers of the Year in 1902.

In the 1901–02 winter, Mitchell toured America with Bernard Bosanquet's team, but left early as he had made arrangements to go to Johannesburg.

Mitchell's first-class cricket career was then at a hiatus, until he returned to captain South Africa in a disastrous campaign in the 1912 Triangular Tournament in England.

For example, he contributed a chapter entitled Forward Play to a book by Bertram Fletcher Robinson, Rugby Football (London: The Isthmian Library, 1896), recently republished in facsimile form.