They contributed fully to an absorbing tussle by twice coming from behind.
But in the end it was to no avail as Grimsby skipper Justin Whittle headed his first goal for the club to net the three points 12 minutes from time.
Another defender, Ronnie Bull, had opened the scoring on seven minutes with his first for the club as Notts got themselves in a defensive tangle.
Impressive midfielder Stefan Oakes scored a tremendous 30 yarder to equalise on 18 minutes, and after twice hitting the woodwork Grimsby went ahead for the second time four minutes into the second-half.
It was a scrappy goal with the Notts defence unable to clear a throw-in, and striker Andy Parkinson squeezed his shot past keeper Wayne Henderson with the aid of a deflection.
Notts roared back and Gavin Gordon scrambled an equaliser from a corner on 70 minutes.
And at that point County probably sensed victory.
But it was the Mariners who finished the stronger, and when midfielder Thomas Pinault floated in a free-kick, the head of Whittle met it and the points stayed at Grimsby.
This was the first of three home games in four for Grimsby, and after getting knocked out of the FA Cup at Exeter, they have won two and drawn one to steadily climb the League Two table.