Second-half goals from Scott Garner and Liam Hearn helped Grimsby come from behind to beat local rivals Lincoln.
gave the Imps a 33rd minute lead after a jinking run, before Garner headed the Mariners level from Michael Coulson's corner.
Hearn's 18th goal of the season just past the hour, latching on to Craig Disley's pass, proved to be the winner.
Anthony Elding hit a post from another corner by Coulson but that miss did not prove costly as Grimsby held on.
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Lincoln City manager David Holdsworth told BBC Lincolnshire:
"In the first half we were fantastic but really we paid the price of not putting the chances away.
"You want that second goal and I think if we'd got that we would have gone on to be worthy winners.
"But that's football, and a 10-minute spell in the second half has cost us."
Grimsby Town joint-manager Paul Hurst told BBC Radio Humberside:
"The first half certainly belonged to Lincoln and I thought we dominated most of the second half and looked dangerous.
"I kind of threw it back to the players at half-time, not to give me excuse of the way the formation Lincoln were playing.
"I just thought we were second best really but thankfully we got a reaction and we played something like we can in the second."