All Black Head Coach, Steve Hansen, selected Barrett for the 2015 Rugby World Cup. Barrett started in one fixture against Namibia, and coming off the bench to cover wing and fullback in the rest. On 31 October 2015, Barrett scored the final try in the 2015 Rugby World Cup Final match against Australia, having been substituted on for the injured Nehe Milner-Skudder. Dan Carter converted his try to make the final score 34–17.