Andrews pulled up in front of the free throw line and released the ball as Buffaloes forward Wesley Gordon tried to contest.
Andrews, a junior, finished with 12 points, seven rebounds and three assists.
His shot gave the Huskies' their third consecutive victory, a stretch that followed a four-game losing streak.
The win improved the Huskies to 14-4 (3-3 Pac 12) and dropped Colorado to 9-9 (2-4 Pac 12).
Washington will play at No. 12 Utah on Sunday.