The Bees struggled to get going in a game where they were second best all over the pitch.
Following three consecutive home wins, Bees fans could be forgiven for expecting their side to come flying out of the box, but the game started slowly with both sides wary of committing too many men forward.
The visitors broke the deadlock on 28 minutes, a defence splitting throughball sent Martin Paterson clear and the on-loan frontman coolly rounded Lee Harrison before sidefooting into an empty net.
The Bees almost equalised two minutes before half-time. Jason Puncheon swung over a long ball from the left which was met by Liam Hatch. The lanky striker got in a powerful header which went inches over the crossbar.
Grimsby came out the livelier after the restart and forced a couple of corners in quick succession. Barnet refused to lie down however and were almost level a minute later.
A corner from the right was swung in by Dean Sinclair. Nicky Bailey rose highest and powered a header towards goal which was somehow cleared off the line by Tom Newey, with keeper Phil Barnes stranded.
The longer the game went on the more likely it seemed that Grimsby would double their lead. Nick Heggarty should have sealed the points with 25 minutes left.
A superb passing move ended with Gary Jones playing the winger in on goal. He tried to slip the ball under the advancing Harrison, but was thwarted by a fine stop.
Harrison almost equalised in the dying seconds when he came up for a corner and narrowly failed to connect with a volley, but in the end it wasn't to be.
The much needed win was Grimsby's first in three away games. They now leapfrog their hosts in the table and it will now be Barnet who are worriedly looking over their shoulders at the relegation places.