Born in Moree, New South Wales, Armstrong played his junior rugby league for the Mungindi Grasshoppers before moving to Goondiwindi, Queensland with his family when he was 12.

[4][5] In 2020, Armstrong signed with the Newcastle Knights and was set to play for their Jersey Flegg Cup team before the season was cancelled due to COVID-19.

[6] He returned to Queensland, playing for the Goondiwindi Boars in the Toowoomba Rugby League, where he scored a hat trick in their 2021 Grand Final win over Highfields.

[8] In 2023, he began training with the club's NRL squad and was named on the extended bench for their round 27 match against the St. George Illawarra Dragons.

[14] In June, it was revealed that Armstrong would be joining English Super League side Leigh Leopards in 2025 on a three-year deal.