First-half goals from Greg Taylor and Paul Arnison were enough to secure victory for Darlington at Grimsby.
The visitors went ahead when Taylor found space inside the area to score his first Quakers goal.
Arnison doubled their lead when he fired a low shot past James McKeown from Taylor's left-wing cross.
Grimsby's Serge Makofo hit an effort high into the roof of the net from Michael Coulson's pass, but they could not find an equaliser.
Grimsby: McKeown, Wood, Kempson, Pearson, Ridley (I'Anson 62), Thompson (Coulson 46), Disley, Artus, Hearn, Duffy, Makofo (Spencer 88). Subs Not Used: Church, Elding.
Goals: Makofo 51.
Darlington: Russell, Purkiss, Miller, Lee, Kris Taylor, Arnison (Bowman 56), Greg Taylor, McReady, Campbell (Bridge-Wilkinson 71), Walshaw, Rundle (Hatch 67). Subs Not Used: Chandler, Atkinson.
Booked: Lee, Purkiss, McReady.
Goals: Greg Taylor 11, Arnison 41.
Ref: Scott Duncan (Tyne & Wear)