Wes Thomas' first-half penalty saw off Cheltenham to earn Grimsby their fourth league win in a row.
The hosts carried a lot of the threat early on in the game, with Thomas and Martyn Woolford going close in the opening ten minutes.
It was Cheltenham who had the best chance during the opening exchanges, though, with Luke Varney firing wide after being found by Chris Hussey's free-kick.
Neither side really threatened for the rest of the first half until, just a few minutes before the break, Hussey pulled Thomas back inside the penalty area, with the Grimsby striker stepping up to squeeze the ball home from the spot.
Neither side really took a grip on the game in the second half, with no real chances to speak of until late on.
Grimsby's Kristian Dennis stung the palms of Robins keeper Scott Flinders, before Cheltenham's Hussey shaved the post from a free-kick on the edge of the penalty area as the Mariners held on to climb to 12th in League Two.
Match report supplied by the Press Association.
