Thornton has spent the 2017-18 season with the Canton Charge, the Cavaliers' affiliate in the NBA G League. He averaged 18.8 points, 3.0 rebounds and 2.9 assists in 37 games for the Charge.
Prior to calling up Thornton, the Cavs announced they sent center Ante Zizic back down to Canton, where he has played 15 games in addition to the 14 appearances he has made for Cleveland.
Thornton has yet to play an NBA regular-season game after the Boston Celtics selected him 45th overall in the 2015 draft. In addition to his G League experience, the 25-year-old played overseas in Australia with the Sydney Kings and then in Italy with Victoria Libertas Pesaro.
Although Thornton has played well in the G League and is shooting 40.4 percent from three-point range, he may not see much time on the court with the Cavs.
Sam Amico of Amico Hoops noted the team needed to sign a 14th player in time for Thursday's game against the Washington Wizards. Thornton gets Cleveland to that number, and his 10-day contract will make it easy for the team to move him back to Canton if it wants to use his roster spot on a proven veteran from the NBA buyout market.