The NBA said his suspension will begin with Monday night's game against the Atlanta Hawks.
Moultrie was assigned to Delaware of the D-League on March 15 after playing 12 games this season. He will also be ineligible to play for Delaware during the suspension.
Moultrie is averaging 3.0 points and 2.9 rebounds. He was the 27th pick in the 2012 draft.
Philadelphia coach Brett Brown declined comment on the specifics of the suspension before his team faced the Hawks.
''Part of that whole collective bargaining is we let the league do what the league has to do,'' Brown said. ''What I will say is, Arnett is still a part of the team and we will reach out to him and help him where we can.''