"It's been a life-long dream of mine to play in the NBA and I've had an incredible experience here at UVa," Anderson said in a statement. "It's really difficult to say goodbye, but I feel I'm ready to make the next step in my basketball career at the professional level."
The athletic 6-foot-6 wing averaged 12.2 points per game in 2014-15 and was a potential All-American before a broken finger sidelined him for the final eight regular-season games.
Virginia lost only one regular-season contest with Anderson in the lineup. He rejoined the Cavaliers for the NCAA tournament, where Virginia lost to Michigan State in the round of 32. The Cavs were considered a top-five preseason team for 2015-16 with Anderson back in the fold.
"Justin has been an outstanding player, ambassador and role model for our program and we'll miss him," Cavaliers coach Tony Bennett said in a statement.
Several NBA executives have told ESPN that Anderson is a likely first-round pick. The last Virginia underclassman to be drafted was Roger Mason in 2002.
Yahoo! Sports was first to report that Anderson was leaving school.
ESPN's Jeff Goodman contributed to this report.