With the Tigers (14-4, 2-0 Ivy League) ahead by 13 with 8:15 to go, the Bulldogs used an 18-6 run to get to 64-63 with 1:30 left.
Yale hit three of its six 3-pointers in the spurt, but could get no closer.
Mack Darrow hit two free throws for 66-63, and Mavraides made 1 of 2 foul shots for the final margin. Morgan missed a 3-pointer with 4 seconds to go.
Tied seven times in the first half, the last at 20-20, Princeton pulled away with a 16-5 run.
Hummer added 12 points and 11 rebounds for the Tigers.
Reggie Willhite led Yale (9-9, 2-2) with 13 points.