A 10-man Grimsby snatched victory at Hayes & Yeading to move within four points of the play-offs places.
Rob Duffy fired the visitors in front when he latched on to the end of Michael Coulson's corner to score.
Shaun Pearson's thumping header from Peter Winn's delivery extended the visitors advantage.
The Mariners' Anthony Church saw red when he fouled Julian Owusu in the box, before Jamie Hand converted the resultant penalty to give Hayes hope.
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Grimsby Town joint-manager Paul Hurst told BBC Radio Humberside:
"Credit to the players, we thoroughly deserved it although we made it hard for ourselves with the sending off.
"The lads have said it probably is a penalty but with the sending off, I'm not too sure.
"There seemed a lot of bodies around but it's one of those you have to live with."