[3][4] Cunningham-South played for the North Harbour under-18s, Canterbury under-19s and Lincoln University in Christchurch, and trained with NZ Warriors in Rugby League.

[12] In January 2025, he scored his first try of season and won player of the match in a 24–7 win over Glasgow Warriors to help his club secure a place in the knockout stages of the 2024–25 Champions Cup.

[16] He was a member of the squad that recorded a fourth place finish at the 2023 World Rugby U20 Championship and scored a try in the semi-final defeat against France.

[18] On 3 February 2024 he made his Test debut coming off the bench as a second-half replacement for Sam Underhill in the opening round of the tournament against Italy at Stadio Olimpico.

[19] Cunningham-South was selected for their 2024 summer tour and scored his first try at senior international level on his first Test start against Japan on 22 June 2024, the opening try of the match in a 52-17 win.