Flagg, 19, received 56 first-place votes, with Charlotte Hornets' Kon Knueppel receiving 44 as the runner-up.
He became just the third player in Mavericks history to win the award (Jason Kidd - 1994-1995, Luka Doncic - 2018-2019) and is the second youngest to win it (LeBron James - 18).
Flagg had a historic rookie season for the Mavericks as the No. 1 overall pick from the 2025 NBA Draft. He became the first rookie in NBA history to score at least 50 points in a game, and the first teenager ever to do so.
He put up at least 40 points in four different games, surpassing James for the most ever by a teenager, and broke the record for most 30-point games by a rookie (11), previously held by Carmelo Anthony with 10.
Flagg became the second rookie in NBA history to lead his team in points (1,473), rebounds (466), assists (316), and steals (84).
The other? Michael Jordan in 1984-1985.
The Newport, Maine native finished the 2025-2026 season averaging 21.0 points, 6.7 rebounds, and 4.5 assists in 70 games.