On 21 April 2017, Kaufusi re-signed his contract with the Storm to the end of the 2019 season. On 6 May 2017, Kaufusi played for Tonga against Fiji in the 2017 Pacific Test, where he started at second-row in the 26-24 win at Campbelltown Stadium. During the season, Kaufusi took over the void second-row position from the departed Kevin Proctor and he took the opportunity by both hands and was instrumental for the Storm to their run leading up to the Finals series where they the winners of the Minor Premiership trophy. On 1 October 2017, in the Storm’s 2017 NRL Grand Final against the North Queensland Cowboys, Kaufusi started at second-row and scored a try in the 34-6 victory. Kaufusi finished his breakout 2017 NRL season with him playing all of the Storm’s 27 matches and scored 9 tries. On 3 October 2017, two days after the Grand Final win, Kaufusi was rewarded with selection in the 24-man Kangaroos squad for the 2017 Rugby League World Cup. On 3 November 2017, Kaufusi made his test debut for Australia against France, where he played off the interchange bench in the 52-6 win at Canberra Stadium.