Match ends, Grimsby Town 0, Wrexham 1.
Joe Clarke effectively ended Grimsby's automatic promotion hopes as his first-half goal saw Wrexham hand the Mariners their first loss in 11 league matches.
With two games remaining, Grimsby slipped six points behind leaders Barnet, who hold a goal difference of plus 14 over them.
Clarke steped a challenge before firing home a left-foot shot from 20 yards.
Grimsby substitute Jon-Paul Pittman almost scored a late equaliser but his header flashed just wide of the post.
Wrexham are now unbeaten in four outings under caretaker boss Carl Darlington.
Grimsby Town manager Paul Hurst speaks to BBC Radio Humberside:
"It was a bad day at the office. The amount of things that were wrong was countless.
"I've got some thinking to do in terms of perhaps why that performance occurred and also now we know our fate in terms of if we are going to win promotion, how it is going to have to be achieved.
"It is frustrating but it is part and parcel of football. We've been on a really good run so I'm not going to suddenly throw the toys out of the pram. But that performance today was poor and there is no getting away from that."
Wrexham caretaker manager Carl Darlington told BBC Radio Wales: "The players... have really worked hard, they've kept to the game plan, the structure.
"First half specifically it was a great performance from us. We didn't lose our shape, we forced them into the errors we wanted to force them into, won the ball back and earned the right to play again.
"It was a great strike by Joe Clarke to score the goal, which came from good combination play... and we've had a couple of half-chances."
- 35RobertsonSubstituted forChapellat 46'minutes
- 7MackrethSubstituted forPittmanat 79'minutes
- 33PalmerSubstituted forHannahat 70'minutes
- 28StorerSubstituted forEvansat 78'minutes
- 29FinleySubstituted forRoperat 89'minutes
- 10BishopBooked at 77minsSubstituted forYorkat 90+2'minutes
- Ian Hussin
- Shots on Target
Second Half ends, Grimsby Town 0, Wrexham 1.
Substitution, Wrexham. Wes York replaces Andy Bishop.
Foul by Jon-Paul Pittman (Grimsby Town).
Rob Evans (Wrexham) wins a free kick.
Foul by Craig Disley (Grimsby Town).
Jay Harris (Wrexham) wins a free kick.
Substitution, Wrexham. Corey Roper replaces Sam Finley because of an injury.
Attempt missed. Andy Bishop (Wrexham) right footed shot from outside the box.
Attempt saved. Jon-Paul Pittman (Grimsby Town) header from the centre of the box is saved.
Foul by Andy Bishop (Wrexham).
Scott Brown (Grimsby Town) wins a free kick.
Attempt missed. Connor Jennings (Wrexham) right footed shot from the centre of the box.
Attempt missed. Jordan Chapell (Grimsby Town) left footed shot from outside the box is too high.
Substitution, Grimsby Town. Jon-Paul Pittman replaces Jack Mackreth.
Substitution, Wrexham. Rob Evans replaces Kyle Storer.
Foul by Scott Brown (Grimsby Town).
Sam Finley (Wrexham) wins a free kick.
Andy Bishop (Wrexham) is shown the yellow card.