ESPN -- The award, named in honor of longtime NBCA executive director Michael Goldberg, is voted on by the NBA's 30 head coaches, with each coach voting for a single winner.
Budenholzer, the NBCA's 2019 winner, has led the Bucks to the league's best overall record at 54-13 and the No. 1 seed in the Eastern Conference.
Donovan has the Thunder sixth in the Western Conference at 41-24 in a season when some wondered whether they could reach the playoffs.
This is the second time the NBCA has had a tie, along with 2017 with Houston's Mike D'Antoni and Miami's Spoelstra.
The NBA also gives a coach of the year award -- the Red Auerbach Trophy -- based on a vote of the league's media. That will be released at a later date.