The result secured a finish in the top 10 for Steve Toyne’s men, who took the lead on 21 minutes through Jon Roper.
His shot from the right evaded the keeper and crept in under the bar.
Twenty minutes later the game was level, Luke Franthorpe running through the home defence to shoot past Andy Thornton.
But 60 seconds after that Dinnington went ahead once more, Liam Cartledge netting from the spot.
It was 3-1 in the second half as Mat Smith’s inviting pass was put through his own net by a Grimsby defender.
And although the visitors pulled one back five minutes from time through Richard Creer, Town held on for the three points.
For the latest Town news see this week’s Dinnington Guardian.