He did not disclose his destination.
Coach John Thompson III made the announcement on the Hoyas' Web site late Thursday.
"We appreciate the hard work he put in at Georgetown, both on and off the floor," Thompson said in a brief statement. "We wish him the best in the future."
The 6-foot-9 inch native of Portsmouth, Va., played in 34 games last season and had per game averages of 3.4 points and 2.1 rebounds.
He was a role player late last season when he made only brief appearances.
Macklin will be the sixth player to leave GU since Thompson was hired in 2004.
His departure means 6-foot-8 inch forward DaJuan Summers will be the Hoyas' only remaining front-court player with extensive game experience next winter.