Dewar first played for the Melrose Club in Wellington and was selected for Wellington province in 1907. In 1908, he was a member of the Wellington team that defeated the touring Anglo-Welsh 19–13 on 27May. The visitors played much of the game with fourteen players, only six forwards, after an injury in the first half: the captains, before the game, had agreed that there would be no substitutions for injury. Dewar and Rush, in particular, as well as Harding and Cracroft Wilson, bore the "heat and burden of a truly Homeric struggle."