In round 4, against Parramatta Eels at the SFS, Tuivasa-Sheck scored his first tries in first grade completing a hat-trick in the Roosters' 50-0 win. On 1 October, he was named Winger of the Year at the Dally M Awards. On 6 October 2013, Tuivasa-Sheck was part of the team that beat the Manly-Warringah Sea Eagles 26-18 for the 2013 NRL Premiership. Tuivasa-Sheck played in 25 matches and scored 9 tries for the Roosters in the 2013.
Playing for the Kiwis in the 2013 Rugby League World Cup, Tuivasa-Sheck made his international debut against Samoa in the 42-24 win at Halliwell Jones Stadium. In the final, against Australia, he injured his leg early in the match and the Kiwis lost 2-34 at Old Trafford. Tuivasa-Sheck played 6 matches and scored 8 tries in the tournament.