Ian Holloway suffered defeat for the first time as Grimsby manager as Exeter earned a narrow 1-0 Sky Bet League Two victory at Blundell Park.
Nicky Law settled the scored midway through the second half as the Grecians moved level on points with Swindon at the top of the League Two standings.
Chances were few and far between during the opening stages.
But the game burst into life when Grimsby midfielder Elliott Whitehouse combined with loanee Anthony Glennon, before curling a chance against the post.
As the clock ticked by, it was the home side who forged more regular openings, but they were indebted to long-serving goalkeeper James McKeown at the other end. He produced a stunning save from Pierce Sweeney.
Upon the restart, Billy Clarke and Harry Clifton both took aim, with the former seeing his header bounce back off the post.
Exeter began to make their mark in the final third – settling the scores after 68 minutes when Law picked Harry Clifton’s pocket before placing the ball beyond McKeown with his left foot.