[1] He previously played for the Highlanders in Super Rugby and Hawke's Bay in New Zealand's domestic National Provincial Championship competition.
Although Mikaele-Tu'u wasn't named in the Highlanders' squad for the 2018 Super Rugby season, he was soon called up as an injury replacement for James Lentjes.
[13] On 1 June 2023, the Highlanders announced on their social media that Mikaele-Tu'u would leave the franchise at the end of the 2023 Super Rugby Pacific season to play in Japan for Mitsubishi Sagamihara DynaBoars.
During the 2023 Bunnings NPC season, he helped the Magpies win back the Ranfurly Shield from Wellington in a tight game that the visitors won 20 – 18.
Mikaele-Tu'u made his debut for Mitsubishi Sagamihara DynaBoars – from the bench – on 9 December 2023 against Hanazono Kintetsu Liners[18] and scored his first try for the club on 17 March 2024 against Toshiba Brave Lupus.
Mikaele-Tu'u was named in the New Zealand Under-20 squad for the 2016 Oceania Rugby Under 20 Championship and played in both matches of that year's series against Australia.
[28] On 5 December 2020, Mikaele-Tu'u - who is of Samoan descent - played for the Moana Pasifika team in a one-off match against the Māori All Blacks in Hamilton.
[29][30] After an outstanding season playing for the Highlanders, Mikaele-Tu'u was, on 10 October 2022, named in the All Blacks XV squad for two matches against Ireland A and the Barbarians during their Northern Tour.