City, with four scholars in the starting line-up, put in a sterling effort against a strong Grimsby side and recovered well after going a goal down when Ian Miller prodded home from a corner with Nicky Nicolau curling home a superb second half effort.
In the end though, after the game finished all-square, it was ex-Imp Anthony Elding who bagged the decisive winner from the spot after Jake Sheridan had seen his effort saved by James McKeown.
City: Jake Turner, Ryan Leggett, Josh Gowling, Tom Miller, Will Rawdon, Frazer Cobb (Cunningham 61), Robert Taylor, Jake Sheridan, Nicky Nicolau, Bradley Barraclough (Oliver 64), Conner Robinson.
subs: Elliot Green, Karl Cunningham, Dan Coupland, Vadaine Oliver, Aaron Rice.
booking: Sheridan (45)
Grimsby: James McKeown, Sam Hatton, Aswad Thomas, Derek Niven, Shaun Pearson, Ian Miller, Joe Colbeck, Craig Disley, Andy Cook, Louie Soares, Greg Pearson.
subs: Anthony Elding, Frankie Artus, Bradley Wood, Dayle Southwell, Andi Thanoj.
goal: Miller (38)
bookings: Niven (36), Soares (45)
Referee: Darren Drysdale
Assistants: Alistair Wilson & Joshua Smith
Fourth Official: Andrew Park
Attendance: 1,469 (812 visiting supporters)
Manager David Holdsworth used this final to cast his eye over a number of players who didn't start the friendly against Gainsborough Trinity at the weekend whilst four second year scholars were also give the chance to impress against a Grimsby side which included personnel with plenty of first team experience.
Trialist Vadaine Oliver, meanwhile, was named amongst the substitutes. The striker was released by Sheffield Wednesday at the end of last season following two years as a professional.
The visiting fans, out in force for their big night in the county capital, were almost silenced in the third minute when a good break from Conner Robinson saw him twist and turn his way into space before finding the advancing Nicky Nicolau who saw his dangerous cross hurriedly hacked away by the Town defence.
Grimsby's first attack saw ex-Imp Greg Pearson go down somewhat theatrically under a challenge from skipper Josh Gowling and although the assistant referee flagged for the infringement he was overruled by Darren Drysdale who spotted nothing untoward. The Town bench duly vented their frustration towards the man in the middle.
The first corner of the game came City's way on the quarter hour mark but Nicolau's delivery to the near post was headed away by a Town defender and as the visitors responded, captain Craig Disley saw a snap shot hit both posts before the ball bounced to safety. Shortly afterwards Pearson prodded a foot wide, although new signing Jake Turner had saved had the effort been on target.
With the Mariners starting to see more of the ball as the half reached its midway point, their first corner was punched clear by Turner whilst at the other end a neat flick from Bradley Barraclough bounced a foot wide following good play by Robinson.
A crunching challenge on Nicolau by Derek Niven earned the Grimsby man a ticking off on the half-hour mark when a yellow card could easily have been brandished in his direction and when Nicolau curled in the resultant free-kick, James McKeown claimed well under pressure from Gowling.
Niven eventually saw yellow for a foul on Sheridan in the 36th minute whilst a couple of minutes later City had Turner to thank as he superbly tipped a low Louie Soares effort wide. The danger wasn't over, however, as from the resultant corner, the ball was flicked goalwards by Ian Miller with Will Rawdon's clearance coming after the ball had crossed the line.
Shortly after the restart a knock to Sheridan saw the City man require treatment and when he was back in the fray, he clashed with Soares following an off-the-ball incident. Before referee Drysdale stepped in, players from both sides got involved in the action until the aforementioned offending duo were cautioned.
HT: Imps 0 Grimsby 1
Both sides emerged unchanged for the second period and it was the visitors who were the first to press forward with Tom Miller forced to clear a dangerous Joe Colbeck cross over his own bar 30 seconds after the restart.
City's response saw Robinson attack before seeing his effort deflect behind and when Nicolau whipped in the corner, Barraclough saw his shot on the turn blocked by a relieved Grimsby defender.
An evenly-matched opening to the half continued, although the Imps were starting to look dangerous on the attack with teenager Robinson particularly impressive up front. On the hour mark Karl Cunningham for Frazer Cobb was the first change of the game.
A smart save from Turner saw him get down well to claim an Andy Cook flick before a Colbeck cross flew a foot in front of Pearson at the back post. Trialist Vadaine Oliver then came on for Bradley Barraclough and his first touch saw him connect with a Rawdon cross only to be denied by McKeown.
Ex-Imp Anthony Elding for Andy Cook was Town's first change before Turner palmed away an Aswad Thomas free-kick. Andi Thanoj then came on for Craig Disley.
As the game entered its final quarter hour, Elding fired two efforts well wide and well over, much to the amusement of the City crowd. The very same fans were on their feet shortly afterwards when the Imps drew level when Robinson fed Nicolau and he did the rest, looking up before curling a superb 77th minute effort past McKeown.
With City pushing for a second, Grimsby calmed things down by bringing on Dayle Southwell for Greg Pearson whilst they were given a further chance when Gowling went down injured before requiring treatment.
As Gowling returned to the pitch, Grimsby won a corner which ended up with Soares having a shot go well over the bar. At the other end Oliver was denied by McKeown with the Town keeper knowing little of the former Sheffield Wednesday striker's shot as it crashed against his back after he flapped at a cross.
Five additional minutes were indicated by the Fourth Official as both sides went in search of a goal in order avoid the lottery of a penalty shoot-out. That goal didn't arrive so penalties it was.
The spot kicks went as follows:-
Taylor (LC) - scored - 1-0
Hatton (GT) - scored - 1-1
Oliver (LC) - scored - 2-1
Soares (GT) - scored - 2-2
Miller (LC) - scored - 3-2
Colbeck (GT) - scored - 3-3
Sheridan (LC) - saved - 3-3
Southwell (GT) - scored - 3-4
Cunningham (LC) - scored - 4-4
Elding (GT) - scored - 4-5
FT: Imps 1 Grimsby 1 (4-5 on penalties)