[1][2] Devan Flanders attended Hastings Boys' High School, where he played First XV rugby alongside future Hawke's Bay teammates Folau Fakatava, Lincoln McClutchie, Danny Toala and Kianu Kereru-Symes.
[7] Flanders made his Magpies debut on 19 August 2018 against Southland and earned his first start against Canterbury on 30 September 2018.
[8] Flanders signed his first contract with the Hurricanes for the 2020 season and made his Super Rugby debut for the franchise on 2 February 2020 against the Stormers.
For his outstanding performance during the series Flanders was rewarded with the Jerry Collins Memorial Bronze Boot.
[20] 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.