Watene-Zelezniak was born in Sydney, New South Wales, Australia, and is of Māori, Tongan and Polish descent.

[9] On 25 September 2015, Watene-Zelezniak was named in Tonga's preliminary train-on squad ahead of their 2017 World Cup qualifying match against the Cook Islands.

His selection came after Matt Moylan, Waqa Blake and Peta Hiku were dropped for disciplinary reasons.

"[17] Watene-Zelezniak made 12 appearances for Wests Tigers and scored 3 tries as the club missed out on the finals by finishing 9th on the table.

[18][19] Watene-Zelezniak only made four appearances for Penrith in the 2019 NRL season as the club finished a disappointing 10th on the table and missed out on the finals.

[21] On 21 January 2021, Watene-Zelezniak announced his immediate retirement from rugby league due to acute kidney failure and associated complications.

[22] On 23 Oct 2023 it was reported that he had made his debut for Poland 40-8 win over North Macedonia in Sydney[23] Malakai Watene-Zelezniak with his brother started a watch Company W Zelezniak.