A stunning free-kick in the last minute secured all three points for Grimsby against a spirited Forest Green side.
The Mariners went in front when Liam Hearn collected Anthony Elding's knock down to score from close range.
But the visitors soon hit back, Yan Klukowski netting from the spot after Gary Silk's challenge on James Norwood.
Sam Russell saved a late penalty from Elding after Jake Thomson's handball but Conor Townsend's free-kick minutes later left him helpless.
VIEWS FROM THE DRESSING ROOM
Grimsby Town joint-manager Rob Scott told BBC Radio Humberside:
"I won't sit here and say that I didn't believe we'd still get three points right until the last minute when we're asking our players to carry on believing.
"We didn't play particularly well first-half but I thought second-half we were by far the dominant team.
"They looked to break on us on the counter attack but I thought we had the better chances.
"Performance wise we probably weren't at the races after we scored."
Forest Green Rovers boss Dave Hockaday told BBC Gloucestershire:
"It's a harsh way to lose a game. I honestly didn't think it was a free kick but we've given the officials the chance to make the decision. It's a tough way to lose but we have to take it on the chin."
"First half I thought we played very well, in the second half we didn't get going and we invited pressure. They stuck two big lads up top and played a simple game and there is nothing wrong with that. We didn't manage the game well enough in the second half."
"We've not come here to become anybody's patsies and for long stretches in the first half they were chasing shadows. I'm just disappointed we weren't braver in the second half, but if we beat Hayes & Yeading next Saturday we'll be back on track again."
Live Text Commentary
Full Time The referee signals the end of the game.90:00 +2:44
Peter Winn produces a cross.90:00 +0:57
Assist by Michael Coulson.90:00 +0:57 Goal scored
Goal! - Conor Townsend - Grimsby 2 - 1 Forest Grn Conor Townsend finds the net with a goal direct from the free kick from just outside the box to the bottom right corner of the goal. Grimsby 2-1 Forest Green.89:53
Luke Graham challenges Michael Coulson unfairly and gives away a free kick.89:37
The referee blows for offside. James McKeown restarts play with the free kick.88:19
Free kick taken by Sam Russell.88:19 Booking
Booking The referee shows Rob Duffy a yellow card for dissent.87:35
Gary Silk crosses the ball in from the free kick, free kick awarded for a foul by Rob Duffy on Eddie Oshodi.87:35 Booking
Booking Jake Thomson receives a caution for unsporting behaviour.87:24
Free kick awarded for an unfair challenge on Andi Thanoj by Jake Thomson.87:02
Rob Duffy has an effort at goal from the just inside the penalty box hitting the post.86:47 Penalty
Penalty taken by Anthony Elding saved by Sam Russell. Grimsby 1-1 Forest Green.85:31
Jake Thomson is penalised for a handball.84:33
Michael Uwezu is ruled offside. Free kick taken by James McKeown.83:31
The ball is swung over by Gary Silk, Luke Graham makes a clearance.81:32
The ball is crossed by Craig Disley, Shot from inside the area by Anthony Elding clears the bar.81:02
Peter Winn sends in a cross, Eddie Oshodi manages to make a clearance.79:29 Substitution
Substitution Michael Pook comes on in place of James Norwood.78:24
Outswinging corner taken by Michael Coulson from the right by-line played to the near post, Keiron Forbes makes a clearance.
Rob Duffy challenges Chris Stokes unfairly and gives away a free kick. Sam Russell restarts play with the free kick.76:11
A cross is delivered by Conor Townsend, clearance by Chris Stokes.73:58
Craig Disley fouled by Keiron Forbes, the ref awards a free kick. Free kick taken by James McKeown.72:55
The ball is swung over by Chris Stokes, Tommy Wright has a headed effort at goal from deep inside the area missing to the left of the target.71:31 Substitution
Substitution (Grimsby) makes a substitution, with Rob Duffy coming on for Liam Hearn.71:31
Centre by Conor Townsend, Close range header by Anthony Elding misses to the right of the goal.70:16
Indirect free kick taken by Sam Russell.70:16 Substitution
Substitution Matty Taylor leaves the field to be replaced by Michael Uwezu.70:16
Free kick awarded for an unfair challenge on Luke Graham by Anthony Elding.69:29
Matty Taylor takes a shot. Save made by James McKeown.68:59
Peter Winn produces a right-footed shot from just outside the box that goes wide right of the goal.67:39
Anthony Elding takes a shot. Save made by Sam Russell.65:44
Free kick crossed right-footed by Jake Thomson from left wing.65:44 Booking
Booking Gary Silk receives a caution for unsporting behaviour.64:47
Corner from the right by-line taken by Michael Coulson, Shaun Pearson takes a shot. Save by Sam Russell. Gary Silk challenges James Norwood unfairly and gives away a free kick.64:03
Tommy Wright gives away a free kick for an unfair challenge on Conor Townsend. James McKeown takes the direct free kick.63:00
The official flags Tommy Wright offside. James McKeown takes the free kick.62:25
The offside flag is raised against Matty Taylor. Indirect free kick taken by James McKeown.61:16
Centre by Peter Winn, Luke Graham makes a clearance.60:44
Conor Townsend delivers the ball, Eddie Oshodi makes a clearance.59:16
Jake Thomson takes a inswinging corner from the left by-line played to the near post.58:17
Jake Thomson restarts play with the free kick.58:17 Substitution
Substitution Liam Henderson goes off and Tommy Wright comes on.58:17
Free kick awarded for an unfair challenge on Matty Taylor by Ian Miller.57:05
Chris Stokes has an effort at goal from just inside the box that misses to the right of the goal.55:50
Liam Hearn takes a shot. Sam Russell makes a save. Corner taken by Michael Coulson, Liam Hearn takes a shot. Jared Hodgkiss gets a block in. Corner taken right-footed by Michael Coulson from the left by-line, Jake Thomson makes a clearance.55:17
The ball is swung over by Liam Henderson, save by James McKeown.53:44
Short corner worked by Jake Thomson.53:37
A cross is delivered by Conor Townsend, clearance made by Luke Graham.49:00
Luke Graham gives away a free kick for an unfair challenge on Anthony Elding. The ball is delivered by Michael Coulson, Andi Thanoj produces a header from the edge of the box and misses to the right of the goal.47:22
James Norwood challenges Liam Hearn unfairly and gives away a free kick. The ball is delivered by Michael Coulson, Headed effort from inside the area by Shaun Pearson misses to the left of the target.45:01
The match restarts for the second half.45:01 Substitution
Substitution Peter Winn is brought on as a substitute for Louie Soares.45:01 Substitution
Substitution Andi Thanoj on for Anthony Church.45:00 +1:11 Half time
Half Time The players leave the pitch at half time.43:39
James Norwood takes a shot. Save made by James McKeown. Outswinging corner taken right-footed by Jake Thomson played to the near post, Header by James Norwood from deep inside the penalty area misses to the left of the goal.42:17
Centre by Yan Klukowski, Shaun Pearson manages to make a clearance.41:40
Gary Silk challenges Matty Taylor unfairly and gives away a free kick. Free kick crossed right-footed by Jake Thomson, save by James McKeown.39:19
Matty Taylor takes a shot. Blocked by Conor Townsend. Inswinging corner taken right-footed by Jake Thomson played to the near post, Michael Coulson makes a clearance. Unfair challenge on Michael Coulson by Matty Taylor results in a free kick. Direct free kick taken by James McKeown.39:02
Yan Klukowski crosses the ball.37:02
The ball is delivered by Chris Stokes, clearance made by Louie Soares.36:01
James Norwood takes a shot. James McKeown makes a fantastic save.34:17
Jake Thomson concedes a free kick for a foul on Anthony Church. Gary Silk restarts play with the free kick. Liam Hearn takes a shot. Blocked by Eddie Oshodi. Corner from the right by-line taken by Michael Coulson, Header by Shaun Pearson from deep inside the penalty area misses to the left of the goal.31:33
Corner taken right-footed by Michael Coulson, save made by Sam Russell.31:10
The ball is delivered by Gary Silk, Luke Graham makes a clearance. Short corner taken by Michael Coulson from the right by-line.29:51
Craig Disley takes a shot. Sam Russell makes a save.24:59
The ball is swung over by James Norwood.23:12
Gary Silk takes the direct free kick.23:12 Booking
Booking Liam Henderson receives a caution.23:08
Liam Henderson gives away a free kick for an unfair challenge on Michael Coulson.22:06
Jared Hodgkiss crosses the ball, clearance by Craig Disley.19:47
Matty Taylor concedes a free kick for a foul on Ian Miller. Conor Townsend takes the direct free kick.19:31
Conor Townsend delivers the ball, clearance by Luke Graham.18:44
The ball is sent over by Chris Stokes, Conor Townsend makes a clearance.17:31 Goal scored
Goal! - Yan Klukowski - Grimsby 1 - 1 Forest Grn Penalty taken right-footed by Yan Klukowski and scored. Grimsby 1-1 Forest Green.16:41
Penalty awarded for an unfair challenge on James Norwood by Gary Silk.15:26
Shot from just outside the area by James Norwood goes over the bar.12:17
Assist on the goal came from Anthony Elding.12:17 Goal scored
Goal! - Liam Hearn - Grimsby 1 - 0 Forest Grn A goal is scored by Liam Hearn from inside the six-yard box to the bottom left corner of the goal. Grimsby 1-0 Forest Green.8:38
Keiron Forbes concedes a free kick for a foul on Louie Soares. Shaun Pearson takes the direct free kick.8:30
Matty Taylor delivers the ball, Gary Silk makes a clearance.6:54
Free kick awarded for a foul by Conor Townsend on Liam Henderson. Sam Russell restarts play with the free kick.0:00
The game begins.
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