First-half goals from Kevin Ellison and Steven Old gave the Shrimps a solid platform and despite a second-half rally from the home side, they never looked like losing their lead.
Grimsby started brightly with lively winger Siriki Dembele playing a low ball across the box that just needed a touch. Luke Summerfield let fly from distance with a shot that flew over the bar.
After the early threat the Shrimps took the lead from their first real opening. Luke Conlan sent in a cross from the left and it bounced nicely for the unmarked Ellison, who had the simple task of looping a header over Jake Kean and into the net.
Michael Rose when tested Kean from a free-kick before the excellent Vadaine Oliver forced the Grimsby keeper into a neat save with a well-worked shot from the edge of the area.
Grimsby’s only reply of note was a Summerfield shot past the post before the Shrimps took control, with Ellison curling an effort wide before being heavily involved in the Shrimps’ second.
Rose swung in a corner which Ellison headed against the crossbar before the ball bounced straight to Old, who bundled it over from close range.
After being booed off at the break, Grimsby came out fighting for the second half and were denied a goal when Danny Collins’ header was superbly cleared off the line by Aaron McGowan.
Dembele then forced Barry Roche into a superb save low to his right with a shot from the edge of the box as Grimsby’s frustration grew.
As the Mariners pushed forward they left gaps at the back and the Shrimps almost took advantage with Keen saving well from Oliver and Ellison, before the latter saw a curling effort cleared off the line by Nathan Clarke with Keen beaten.
Grimsby continued to press but the Shrimps defended superbly and collected another valuable three points.
Grimsby: Kean, Mills, Davies, Clarke, Collins, Rose (Jaiyesmi 82), Dembele, Summerfield, Woolford, Matt (Vernon 76), Jones (Hooper 60). Subs (not used): Killip, Dixon, Osborne, Berrett
Morecambe: Roche, Old, Müller, Lavelle, McGowan, Conlan, Kenyon, Rose, Lang (Wildig 61), Oliver, Ellison (Thompson 89). Subs (not used): Maher, Brough, Lund, Campbell, McGurk