The England U21 international has agreed to a deal with Forest that will keep him at the club until 2030.
McAtee expressed his excitement about joining Forest, saying he is ready for a new challenge and looks forward to working with his new teammates.
Forest's Chief Football Officer, Ross Wilson, welcomed McAtee to the club, praising his talent and expressing the team's ambition to achieve great things together.
Wilson also highlighted the strong interest in McAtee from other clubs, but praised his determination to join Forest.
McAtee's signing is seen as a significant boost to Forest's squad, with the team now having three young talents from the England U21 European Championship-winning team.