Mitch Rose's first-half goal was enough to give Grimsby a 1-0 win over 10-man Forest Green at Blundell Park.
The midfielder followed up on Sam Jones' missed penalty after Jack Fitzwater was sent off for the visitors.
Grimsby had the majority of the play during the first half, with Jones sending an effort over before Luke Summerfield forced Bradley Collins into a smart save.
The hosts were eventually rewarded for their efforts when Diallang Jaiyesimi was hauled down in the box by Fitzwater, leading to the defender's second yellow after 37 minutes.
Jones saw his penalty saved by Collins, but Rose was quickest to the rebound and tucked the ball away to give the hosts a deserved lead.
Forest Green almost got themselves back into the game just after the break when Jamille Matt was forced to clear off the line from a corner.
Grimsby almost doubled their lead when Jones' header came back off a post, but they held on to their lead to record a third straight league win.