No terms of the deal were disclosed, but Philly.com cited multiple sources which said it is worth approximately $43 million over five years.
"We are very happy to have reached a tentative agreement with Thaddeus, who we consider to be an integral part of our long-term plans," Sixers president of basketball operations Rod Thorn said. "Thad has thrived in his role under coach Collins and we are happy to have him back with the Sixers."
The 23-year-old Georgia Tech product excelled off the Sixers bench last season, averaging 12.7 points, 5.3 rebounds and 1.0 assists per game while appearing in all 82 contests.
Young was the 12th overall pick in the 2007 NBA Draft.