Grimsby came from behind to beat Port Vale 2-1 in Neil Aspin's first game in charge at Vale Park.
Vale took the lead after 39 minutes when James McKeown pushed the ball to the feet of Tom Pope, who poked it in.
Sam Jones equalised for the Mariners in the 50th minute, heading home following a corner.
Sixteen minutes later Sirki Dembele rounded Kelle Roos to walk the ball over the line and claim his first goal in Mariners colours.
Substitute David Worrall came close to earning Vale a share of the points but his shot in the 89th minute was pushed just over the bar.
A minute later Nathan Smith could have been the hero as the ball sat up for him but he sent his volley flying over.