A single goal from Phil Jevons, a £250,000 summer signing from Everton, was enough to send Grimsby to the top of the First Division, the first time they have headed the game's second tier since 1982.
The Mariners may find themselves on the crest of a wave only because this was the one match in the division to survive international call-ups, and come the end of the season these three points may count for more in the relegation stakes, but they deserve them.
Barnsley were the better side but Grimsby's defensive resilience makes up for what they lack in flair. In the end the victory was comfortable enough as Barnsley had their goalkeeper, Kevin Miller, sent off seven minutes from time.
That was the end of an eventful afternoon for the goalkeeper, who may have created a record for the number of different shirts worn by a player in one match. His original black one clashed with Grimsby's strip, the green one which replaced it made him look like one of the officials, and he ended up wearing a fetching shade of mustard borrowed from Grimsby's kit bag.
It was not his lucky colour. Almost the first thing he did in it was pick the ball out of his net after Jevons' goal on 22 minutes. Jonathan Rowan jinked his way into the penalty area and slipped the ball to his striking partner, who drove it low to Miller's right.
Barnsley's fires have cooled since their short-lived elevation to the Premiership, when their fans compared them to Brazil. They now resort to the long ball more often, though they are still capable of some neat football, and in the Dutchman Dean Gorre they have a useful playmaker.
They created the bulk of the early chances, the best coming when Bruce Dyer's header was kicked off the line and Mike Sheron drove the loose ball over the crossbar. The pair also let a stream of lesser opportunities go begging through wayward finishing with boot and head, and some timely blocking from Grimsby's well organised back four.
The Mariners have got where they are today by making the most of slender resources. In the absence of outstanding talent they get by on discipline and organisation, qualities that enabled them to sit on their lead despite relentless Barnsley pressure in the second half, orchestrated by the substitute Mitch Ward.
Grimsby pulled nine men back behind the ball whenever Barnsley crossed the halfway line, their offside trap was well oiled, and on the rare occasions their opponents sighted goal Sheron and Dyer were found wanting.
As Barnsley's frustrations grew so did the possibility of Grimsby increasing their advantage on the break. Miller saved well when Jevons broke down the right but when he raced out to intercept Alan Pouton, who was clear on goal, seven minutes from the end, he missed the ball, hit Pouton and was off.
With only 10 men there was no way back for Barnsley, and despite a glaring miss by the substitute Wayne Burnett Grimsby's boat had come in.
Grimsby Town 1 Barnsley 0
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