Martin Paterson's first-half strike was enough for Grimsby to see off fellow strugglers Barnet.
Paterson had already gone close with an overhead kick before he gave the Mariners the lead after 27 minutes.
The striker, on loan from Stoke, latched onto Nick Hegarty's through-ball before rounding keeper Lee Harrison and slotting home.
Barnet's Nicky Bailey had a header cleared off the line before Paterson hit a post with a low shot.
Barnet: Harrison, Devera, King, Yakubu, Gross (Vieira 68), Cogan (Graham 69), Sinclair, Bailey, Puncheon, Birchall, Hatch (Warhurst 83).
Subs Not Used: Flitney, Charles.
Grimsby: Barnes, Croft, Fenton, Whittle, Newey, Till, Pulis, Hegarty, Ravenhill, Jones, Paterson.
Subs Not Used: Murray, Rankin, Harkins, Boshell, North.
Booked: Croft, Hegarty.
Goals: Paterson 28.
Ref: P Armstrong (Berkshire).