The surgery was performed at Stanford Medical Center in Palo Alto, California, by Dr. Jeffrey Yao, a specialist in hand, wrist and elbow surgery.
Valanciunas will be in a cast for four weeks, and then his status will be re-evaluated.
Valanciunas' injury occurred in the second quarter of Wednesday's victory over the Golden State Warriors. Valanciunas was posting up Draymond Green when, as he turned to make a move, Green swiped down at the ball and hit him on the hand.
The backup center immediately fell to the ground in agony, then got up holding his hand while in visible pain. A trainer spent time working on Valanciunas along the bench before eventually escorting him to the locker room.
Valanciunas is averaging 12.8 points and 7.2 rebounds per game for the Raptors, who have the best record in the NBA at 23-7.
ESPN's Tim Bontemps contributed to this report.