The tournament's third seed, Oregon (24-8) found itself in a fight from the start against the sixth-seeded Huskies. The Ducks stopped Washington from getting off a shot in the closing seconds of regulation and held on in overtime to reach Friday's semifinals against No. 10 seed Utah, which knocked off No. 2 California in overtime earlier Thursday.
A year ago, Washington (18-15) became the first team from a power conference to miss the NCAA tournament after winning the regular-season title, thanks to an opening loss to Oregon State in the Pac-12 tournament. The Huskies could be out of the bracket after coming up short again in this year's tourney.
C.J. Wilcox led Washington with 19 points, Scott Suggs added 18 and Abdul Gaddy had 14 with five rebounds and five assists.
Damyean Dotson had 17 points and E.J. Singler added 16 for the Ducks.
Wilcox put Washington up 64-62 on a turnaround with 50 seconds left in regulation, and Oregon's Johnathan Loyd hit two free throws to tie it. Washington had a final chance in regulation but fumbled the ball away without getting a shot.
In overtime, Kazemi scored six straight points, with his two-handed slam on the break putting the Ducks up 72-65. He then followed a basket by Suggs with a three-point play that made it an eight-point game.
Oregon was the early front-runner in the Pac-12 race before a few slip-ups knocked them to the No. 3 seed.
The Ducks started the season 18-3 and won their first seven conference games before losing three straight. Oregon won five of the next six but closed with road losses to Colorado and Utah to drop out of the rankings.
It was a disappointing finish, but the Ducks' season still was good enough to earn Dana Altman coach-of-the-year honors in the Pac-12 and Oregon a likely spot in the NCAA tournament.
Washington played a wild opening game of the Pac-12 tournament, blowing a 19-point second-half lead and a 15-point advantage with 8:35 left before pulling out a 64-62 win over rival Washington State.
Oregon swept the season series, beating Washington by five at home and by 13 in Seattle.
Round 3 began as an offensive shootout. Washington went on an 11-0 run to go up 23-14 and hit 13 of 27 shots in the first half. Oregon answered with a 13-4 run to tie it and shot 14 of 28 before halftime.
Both made 4 of 6 from the 3-point line, with Oregon going into the break with a 39-34 lead.
The shooting fell off early in the second half, but both teams were struggling, so the game remained close.