The hosts went in front in the very first minute through Luke Waterfall, who headed Ryan Williams’ corner into the net.
There was an appeal for a penalty when Shaun Pearson appeared to handle the ball in the Grimsby box, but the referee was unmoved.
Grimsby levelled just before the break when Greg Pearson struck from 20 years, beating Jason White in the Gainsborough goal.
But the home side regained the lead on 56 minutes, Paul Connor taking advantage of an error and tapping into the empty net.
There were chances at both ends as Anthony Elding put the ball wide from 12 yards for the Mariners and Connor sent one over the bar from Williams’ right-sided cross.
Substitute Terry Hawkridge drilled a shot straight at the keeper after receiving Jonathan Williams’ pass.
With five minutes left to play a long range effort from Sam Hatton deflected off Danny Hone and went past White to bring Grimsby level once again and the game ended without another goal.