LEE Molyneux's third goal of the season earned the Shrimps revenge for an opening day defeat to the Mariners.
The wing-back struck within just two minutes to send the Mariners to their third loss in four games on the road, and send the Shrimps above them in League Two.
The Shrimps made three changes to the starting line up with Molyneux back in the side and making the most of his opportunity with a goal within the opening two minutes.
Michael Rose's corner was met by Molyneux on the edge of the box, and the wing-back's shot made it all the way through the crowd of players and past the diving James McKeown to give the Shrimps an early lead.
Looking to quickly make amends, Gavin Gunning was found inside the box from a cross on the right, but he could only direct his header straight at Barry Roche in the Morecambe goal.
Danny Andrew looked to catch the hosts' stopper out after Zak Mills was brought down by Antony Evans on the right, but the full-back's free-kick sailed wide.
The Shrimps then went close again when Chris Clements cleared an Andy Fleming volley off the line after two successive corners for the hosts.
A good passing move then saw Jamey Osborne presented with a chance on the edge of the box for the visitors, but the midfielder could only drag his shot wide of the target as the Mariners remained 1-0 behind at the break.
Morecambe had the ball in the back of the net soon after the break, but Paul Mullin was flagged for offside as he curled the ball beyond McKeown.
Kevin Ellison was presented with a good opportunity when the ball fell to him in the box, but Shaun Pearson managed to get his body in the way just as the experienced winger got his shot away.
And Mullin had another chance moments later as he tried his luck from 25 yards out, but McKeown managed to beat the ball away from danger.
The Shrimps were unlucky not to extend their lead when Evans made his way into the box from the right and chipped the ball up to Mullin, who somehow managed to plant his header onto the crossbar from just a few yards out.
Some great work down the right from Callum Dyson resulted in the ball falling to Clements on the edge of the box, whose shot was deflected before Tom Bolarinwa won a corner.
From the set-piece, Danny Collins flicked the ball on for Shaun Pearson, who shot over under pressure from a Morecambe defender – and the Town defender was adamant that he should have had a penalty.
Mullin had another opportunity as he broke clear of the Town defence, but after looking set to round McKeown, the keeper recovered well to knock the ball away.
Town had a late chance to pick up a point from their visit to Lancashire when substitute Ben Davies' cross fell to Andrew at the back post.
But the left-back's volley drifted over the bar and - after Ellison had a late goal ruled out for offside - the Mariners were sent home once again without a point.
Morecambe: Roche, Wakefield, Edwards, Whitmore, McGowan, Rose, Fleming, Mullin (Turner 85), Evans (Wildig 70), Molyneux, Ellison. Subs not used: Nizic, Conlan, Duckworth, Hedley, Jordan.
Grimsby: McKeown, Mills, Pearson, Collins, Andrew, Bolarinwa (Yussuf 83), Gunning (Davies 80), Osborne (Asante 65), Clement, Dyson, Jones. Subs not used: Disley, Boyce, Comley, Maxwell.
Ref: D Handley