Flavell, who replaces Pero Cameron, is already a familiar part of the Tall Blacks programme as both a player and coach.
He wore the black singlet for 38 games from 1999-2002, including the 2002 world championships at which he helped lead New Zealand to a memorable fourth place.
After turning to coaching, Flavell spent 13 seasons as an assistant with the New Zealand Breakers, winning four championships during a five-year stretch, before joining the South East Melbourne Phoenix as an assistant for three seasons.
He has also served as head coach for the New Zealand under-18 team (2013), as Junior Tall Blacks assistant coach (2014) and as Tall Blacks assistant coach (2020).
At the domestic level, Flavell won NBL titles with the Auckland Pirates (2012), the Southland Sharks (2018) and the Canterbury Rams (2023 and 2024).
Flavell joins a Tall Blacks programme ranked 22nd in the world.
New Zealand finished third overall at the 2022 Asia Cup, and 22nd at last year’s Fiba World Cup.
Flavell said it was an honour to take over the reins of the Tall Blacks.
"There’s a lot of emotions that came up for me, because I feel so passionate about the black singlet, about the Tall Blacks, what we’ve done and achieved on the international stage in the past.
"And also seeing where we are currently at with the programme; you can’t help but get excited looking ahead at the pool of talent that we have coming through with the youngsters.
"For me, it’s been a long journey, coming from being part of the Tall Blacks programme as a player — growing up and having that dream of putting on the black singlet — and then being involved in some of our finer moments in 2001-02, then being an assistant coach.
‘‘I feel really feel privileged and honoured to be given this responsibility."
Basketball New Zealand chief executive Dillon Boucher said Flavell had the right mix of character and experience to help lead the Tall Blacks to success in the coming cycle.
"His passion for the jersey and for New Zealand basketball is as high as you can get," Boucher said.
"He has enjoyed recent success with back-to-back titles with the Rams ... and knowing what Judd is capable of, I’m excited to watch him lead this exciting group of players we have right now."
