Grimsby made it two home wins out of two as they finished off a good week's work.
After seeing off Wigan in the Carling Cup in midweek they were comfortable winners against a Mansfield side tipped by many to be favourites for automatic promotion this season.
But they way Grimsby are playing they should be up there themselves once they start picking up points away from home.
At Blundell Park sides are going to find it difficult to pick up anything, for apart from Boston who gained a 1-1 draw, Bury and now Mansfield have fallen to the Mariners.
Grimsby made the best possible start albeit with a large slice of good fortune.
Their fifth minute corner taken by John McDermott was played back to French midfielder Thomas Pinault whose shot from outside the box took a deflection before nestling in the back of the net.
Striker Andy Parkinson ought to have made it two a couple of minutes later but his close-range shot was blocked by Mansfield keeper Kevin Pilkington.
The visitors came back and proceeded to miss some good chances before losing their heads before half time when they had three players cautioned.
Grimsby were the better side in the second half but at 1-0 there was always the chance that Mansfield could equalise.
The home side needed a second goal but it did not arrive until four minutes from time.
By throwing men forward Mansfield were caught out at the back, and when Parkinson knocked a glorious ball through, wing-back Jason Crowe ran almost half the length of the field to score his first goal for the club.