Playing their first home league game since grabbing a late win over high-flying Leicester a month ago the Gills completed their sixth home win of the season with the match over as a contest by half time.
The home side were two up within the first 15 minutes against a disappointing Grimsby side who were unable to build on last weeks 2-0 success against fellow strugglers Stoke, their first win of the year.
Rod Wallace scored both. The first after six minutes finished a move involving Roland Edge and Paul Shaw leaving Wallace to fire home a low drive past Danny Coyne.
Grimsby player manager Paul Groves then saw his fierce 25 yarder tipped over by Jason Brown before Grimsby conceded a second four minutes later.
Hampered by a troublesome hamstring injury Wallace has been unable to get a consistent run of games in the side but notched his second of the afternoon with a neat lob over Coyne, as he raced onto a long punt up field by defender Chris Hope.
Coyne was caught in no-mans-land as Wallace ran to the goal line making sure the ball found the net as Guy Ipoua tried hard to get the final touch himself.
Christopher Thompson saw his low effort saved by Brown but Gillingham finished the half well as Chris Hope headed home only his second goal of the season and his first in the league.
The Gills won a free kick on the right and after referee Paul Taylor had ordered it to be re-taken Nicky Southall crossed from the right for Hope to plant a firm header past Coyne.
The second half was a much tamer affair, although Coyne did well to block a goal bound effort from Gills player-manager Andy Hessenthaler who was one of six players booked by referee Paul Taylor.
The downside for Hessenthaler is that he now faces a two match ban which will keep him out of home games against Brighton and Nottingham Forrest early next month.