The contract, according to Bartelstein, will be for six years, $41 million.
Blount, an unrestricted free agent, was wooed by several teams, notably the Heat and 76ers, but in the end felt like he needed to return to Boston.
"I think Danny [Ainge] and Doc [Rivers] did a great job of convincing him that he would be part of great future in Boston," Bartelstein told Ford. "They stepped up to the plate offering their full mid-level exception and I think at the end of the day, Mark felt like they really wanted him the most."
Blount's contract also includes a 15-percent "trade kicker," meaning that if Blount is traded at any time during the length of the contract, he will receive an additional 15 percent of his remaining salary on top of the salary, a source told ESPN's David Aldridge.
The Sixers made Blount an offer last week, hoping he would want to be reunited with his former Celtics coach, Jim O'Brien, who is now Philadelphia's head coach.
The Sixers may now turn their attention to free-agent forward Brian Skinner, a former 76er who played in Milwaukee last season.
The 7-foot, 250-pound Blount was Boston's only significant
unrestricted free agent. The four-year veteran appeared in every
regular season game for the Celtics last season, averaging 10.3
points and 7.2 rebounds per game.
Blount was second in the league in field goal percentage behind
Shaquille O'Neal, making 56.6 percent of his shots.
In a March game against the Orlando Magic, Blount scored 28
points and had a career-high 21 rebounds, the most rebounds by a
Celtic in a decade.
Information from The Associated Press was used in this report.