Terms of the deal were not announced.
The 6-foot-9, 205-pound Zagorac has played professionally in Serbia since 2011. The native of Belgrade, Serbia, started 23 of 26 games for KK Mega Leks in the Liga ABA where he averaged 15 points and 6.5 rebounds last season after being named the league's MVP in 2015-16. He also started 11 of 12 games in Serbian BCL play.
Boston originally drafted Zagorac with the 35th pick overall in the second round before trading his rights along with the draft rights to Deyonta Davis to Memphis for a 2019 first-round pick.