The NCAA was looking into amateurism issues involving the 7-foot, 245-pound Serbian big man since he played limited minutes in the Adriatic League and the EuroCup, a source told ESPN.
Ristic never signed a pro contract and wound up spending last season at Sunrise Christian Academy in Wichita, Kan.
Ristic will give Arizona coach Sean Miller a different look than the other big men in the program. He's long and skilled -- and is able to score in the low post and also step out and make shots from the perimeter. He was the MVP of the Nike International Junior Tournament in 2013 after averaging 17.7 points and 9.5 rebounds per game.
The Wildcats are ranked No. 2 in the country in the Associated Press preseason poll that was released on Friday.