Samardo Samuels led Cleveland with 14 points and Donald Sloan added 13. The Cavaliers had six players score in double figures.
Bobby Brown scored a game-high 22 points for Siena while Matt Janning added 21.
Irving, who broke his right hand practicing with the summer league team in July, played 21 minutes and had three assists.
Dion Waiters, taken by Cleveland with the fourth pick in the draft, scored 11 points off the bench. C.J. Miles started at shooting guard and scored 10 points. Cavaliers coach Byron Scott said before the game Waiters would have to earn a spot in the starting lineup. Waiters entered the game in the second quarter and his first shot was an airball.
