A statement Sunday from the Manning Passing Academy says Manziel had missed some assignments and was late to others and said he was feeling ill.
The statement emailed by camp spokesman Greg Blackwell says officials agreed "that it was in everyone's best interest" for Manziel to leave a day early Saturday.
The Texas A&M quarterback is the only freshman to win the Heisman Trophy.
Former Saints quarterback Archie Manning and his two NFL QB sons - the Broncos' Peyton and the Giants' Eli - hold the camp at Nicholls State in Thibodaux (TIB-uh-doh).
The camp began Thursday and ended Sunday.