Ross Hannah's goal fired Grimsby to the top of the Blue Square Bet Premier as they beat Wrexham.
Victory sent the hosts above Newport County, while Wrexham fall to third, following a superb advert for English football's fifth tier in which both sides gave their all.
Adrian Cieslewicz threatened on several occasions for the visitors, but was denied by James McKeown.
Hannah's 77th-minute close-range strike settled it in Grimsby's favour.
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Wrexham boss Andy Morrell told BBC Radio Wales: "It could have gone either way. Looking at it we were really good. We defended well as a unit.
"I thought we were solid. I didn't think they caused us too many problems and I think we probably nicked the first-half as well.
"I thought we had the better chances and could probably have gone in [at half time] in the lead.
"But they probably nicked the second half, had a bit of pressure on us and there were a couple of mistakes [from us] and we conceded."