A strong second-half revival by Terry Hyland's Leitrim came up just short in their concluding Division 4 North game on Sunday at Corrigan Park in Belfast.
Antrim let slip an 11-point lead against their opponents before Tomas McCann's late point clinched a 2-17 to 1-19 win.
The Saffrons had already confirmed top spot before the game at a sunny Corrigan Park and they will secure promotion if they beat Waterford in two weeks time.
Goals from Conor Stewart and Conor Murray helped the hosts to a 2-14 to 0-9 lead early in the second half.
Leitrim fought back and levelled before McCann popped up with the late winner.
Leitrim now face Wexford in a Division 4 shield semi-final on June 12/13th.