On 11 August 2016, Walker-Leawere was named in the Wellington Lions squad.[8] He made his Mitre 10 Cup debut against Hawke's Bay, nine days later.[9] He went on to play three seasons for Wellington.
The Hawke's Bay Rugby Union announced on 7 June 2019 that Walker-Leawere had signed a three-year contract to play his provincial rugby for Hawke's Bay.[10] He made his Magpies debut against Manawatu on 11 August 2019.
Meanwhile, in November 2017, the Hurricanes announced that Walker-Leawere had signed a two-year deal with the franchise, and named him in their squad for the 2018 Super Rugby season.[11][12] He missed the first part of the season as he was initially recovering from shoulder reconstruction surgery and then suffered a knee injury. He made his Super Rugby debut for the Hurricanes against the Brumbies, on 30 June 2018.[13] He has since re-signed with the Hurricanes multiple time, most recently recommitting to the franchise until the end of the 2026 season.[14]
In 2017, he enjoyed more success with the New Zealand Under 20 team. He was named in the squad for the 2017 Oceania Rugby Under 20 Championship, which that year consisted of tests against Australia, Fiji and Samoa.[19] He played in two of the three games, and New Zealand retained the Oceania title.[20]
In 2018, Walker-Leawere - who is of Ngāti Porou descent - was a member of the Māori All Blacks squad that toured the United States, Brazil and Chile.[23] He made his Māori All Blacks debut on 3 November 2018 against the USA and scored two tries in that game.[24] In July 2019, he was named in the squad again for a two-test series against Fiji.[25] On 5 December 2020, he played for the Māori All Blacks in a one-off match against Moana Pasifika in Hamilton.[26]
Having trained with the All Blacks a few months prior after being called up as injury cover for Patrick Tuipulotu,[27] Walker-Leawere was on 8 October 2024 named in the All Blacks XV squad for two matches against Munster and Georgia.[28][29] He made his debut for the team on 2 November 2024 in the game against Munster, which ended in a 38–14 victory to the All Blacks XV.[30]