Harrogate inflicted a first Sky Bet League Two defeat on Grimsby manager David Artell as they won 2-1 at Blundell Park.
Goals from Liam Gibson – against his former club – and Matty Daly did the damage before Kieran Green netted a late consolation.
Grimsby had the first noteworthy chance in the 15th minute when Danny Rose curled narrowly wide after cutting inside on his right foot.
At the other end, goalkeeper Harvey Cartwright was called into action with a fine double save from Harrogate winger Abraham Odoh.
His team-mate George Thomson went close twice in quick succession as Harrogate enjoyed a dominant spell before half-time, with Gibson heading in from a corner to put them 1-0 up.
Rose skied a header in the 47th minute after being picked out by Anthony Glennon as Grimsby pushed for a leveller.
Harrogate passed up two half-chances to put the game to bed before getting their second goal through Daly in the 72nd minute, while Green offered Grimsby hope with a low drive that came in time added on.