[1] In his youth career, he played for the Wesley College first XV and was Head Prefect, captaining the team in his last year of school.

[5][6] Vaa'i debuted for New Zealand on 11 October 2020, replacing Patrick Tuipulotu off the bench, in the 75th minute, in a 16-16 draw against Australia.

The following week, with Sam Whitelock ruled out due to concussion symptoms, Vaa'i made his first start for New Zealand, with the All Blacks going on to beat Australia 27-7.

Following Tuipulotu's illness ahead of Bledisloe IV a fortnight later, Vaa'i was restored to the matchday 23, accompanying debutants Will Jordan, Asafo Aumua, and Cullen Grace on the bench.

Vaa'i became a regular starter for the Chiefs in 2021, finishing the season with a total of 19 Super Rugby caps.