Andi Thanoj's first senior goal for Grimsby earned them a dramatic draw to kill off Wrexham's automatic promotion hopes at the Racecourse.
The result confirmed Fleetwood's promotion, leaving Wrexham to rely on the play-offs.
Chris Westwood thought he had won it with a close-range 72nd minute header after Jake Speight's opener was cancelled out by Anthony Elding.
But Thanoj struck from outside the penalty area to deny the hosts.
VIEWS FROM THE DRESSING ROOM
Grimsby Town joint-manager Paul Hurst told BBC Radio Humberside:
"If we'd have won today, we'd have still been in with a chance [of making the play-offs].
"What we're coming away with is the knowledge that we've more than competed with a team that's done extremely well this season.
"[They] will go into the play-offs probably as favourites and we've shown we can compete with the best in the league."