Johnston signed for
Major League Rugby side
New England Free Jacks ahead of the
2021 Major League Rugby season. He had previously represented in the 2019 and 2020 seasons of the
Mitre 10 Cup, while he was also selected to play for the
China Lions in the
2020 Global Rapid Rugby season. Johnston would appear in 14 games during the
2021 season and 17 games during the
2022 season. Scoring 3 tries both seasons. Then during the
2023 season Johnston would appear in 17 games for the free jacks scoring 2 tries. Being a key part of helping the team win their first ever
MLR championship. He would then join Waikato to finish out the 2023 season. In
2025 he would rejoin the frees jacks and claim his 50th cap for the team on February 3. Captaining the team Johnston would help the free jacks win their 3rd straight
MLR championship appearing in 19 games and scoring 2 tries. ==Honours==