Rumarn Burnell gave the visitors a first-half lead, but a second-half strike from Jimmy Knowles and a late James Tague effort ensured Stags maintained their winning start in the Youth Alliance Cup.
The Stags struggled to make their dominance count in the first 45, but produced a sensational second half display to turn the game around and collect all three points, meaning they sit top of Group 4, having collected six points from their opening two games.
The Mansfield starting XI saw two changes from the side that lost 4-2 to Doncaster last Saturday. Nathan Saunders made his first start of the season, in for Riley O'Sullivan, and Warren Squires replaced Keaton Marrs in the Stags' goal.
A tentative first 20 minutes from both sides meant that either 'keeper had little to do, as most of the battles were taking place in the centre of midfield.
Jamie Chisholm was making himself known to Burnell, when on 23 minutes, the Grimsby forward got in behind the Stags' back line in the left hand channel. As the number nine drove towards goal, Chisholm tracked his man all the way and put in a perfectly timed sliding tackle.
Generally, it was a quiet first half, with perhaps Stags' best chance falling to Rhys Sarson in the 25th minute. Tyrese Sinclair whipped in a wicked in-swinging corner from the left-hand side which Sarson met in space at the near post. The Stags' number nine got decent contact, heading the ball down low to the goalkeeper's right, but unfortunately the ball went just the opposite side of the 'keeper's near post.
With 28 minutes gone, Grimsby put together a neat attacking move, with a diagonal ball being lofted over the Stags' defensive line from the right-hand side which released Conley Poynter down the left. The forward took the ball to the byline before dinking a dangerous cross in towards the back post. Under pressure, with opposition attackers looking to get on the end of the cross, Jordan Armsden produced some acrobatics with a bicycle-kick clearance from underneath his own crossbar, removing the danger.
Sinclair had a half-chance on 33 minutes, after a long goal kick from Squires found the forward through on goal. With the ball holding up and defenders closing in, Sinclair was forced to take his effort early as he sliced through his attempt, directing the ball high and wide of goal.
The deadlock was broken by the visitors in the 40th minute as Burnell latched onto a scooped ball over the top, and somehow managed to squeeze the ball in from the acutest of angles to give the away side a 1-0 lead going into half-time.
The second half began with a newfound energy from the Stags. Just a minute from the restart, Sinclair was first to test the Grimsby 'keeper, with a swerving free-kick from 30 yards, which the goalie looked happy to be able to hang onto.
Sarson, Tague and Knowles then combined down the right in a quick counter-attack, but perhaps a pass too many meant that the move was halted by a defender's interception.
Moments later there was a penalty appeal for the Stags as Sinclair was bundled to the floor, with what what sounded like clear contact, but the referee waved away any protests as Stags continued to push for an equaliser.
With 63 minutes gone, Stags found their much-deserved equalising goal. Tague, playing in a slightly more forward position, cleverly nut-megged the Grimsby midfielder before feeding Sinclair to feet on the edge of the opposition area.
Sinclair played a beautifully weighted through ball to the back post, as both Sarson and Knowles looked to get the end of it. Sarson met the ball well, but his strike cannoned off a Mariners defender into the path of Knowles, who showed excellent composure as he calmly swept the ball in for 1-1.
With 76 on the clock Knowles produced a splendid piece of skill to burst away from two defenders, but his strike from the edge of the area flashed by the outside of the goalkeeper's far post.
Grimsby then nearly got a second against the run of play as Burnell found space at the back post following a Brandon Buckley corner, but the forward was unable to sort his feet out in time and saw a good opportunity spurned late on.
On 85 minutes, Sarson played a sumptuous through ball for Tague, who collected it in his stride, got the ball out of his feet and tucked home the winner for the Stags late on to give them all three points.
The referee blew for full time and the Stags now sit top of Group 4, with an away game to Fleetwood Town their next cup fixture, and victory there could all but seal their qualification into the knockout stages.
STAGS’ XI: Squires, King, Davis, Cornell (c), Armsden, Chisholm, Sinclair (O'Sullivan 82’), Tague, Sarson, Saunders, Knowles.
SUBS NOT USED: Marrs, Langton, Ingram, Stokes.
GRIMSBY XI: Battersby, Jamieson, Saunders, Curran, Pollock, Powles, McPherson (Painter 62'), Richardson (Stead 70'), Burnell, Buckley (c), Poynter.
SUBS NOT USED: Starbuck, Adland, Derrick.