The talented center's father confirmed the news to SI's Luke Wynn on Wednesday afternoon.
Papagiannis spent his junior year at Westtown (PA) School before departing for Greece last summer. He played in 2014-2015 with Panathinaikos and will stick with the club.
The 7-foot-1, 270-pounder had considered NC State, St. John's, Oregon, and Kentucky. He recently suited up for Greece in the FIBA U-19 Championships and averaged 8.1 points, 7.7 rebounds, and 2.6 blocks in 21 minutes per game.
NC State currently has eight eligible scholarship players on the 2015-2016 roster and are still pursuing talented wing Maverick Rowan.