After drawing the first leg of their semi-final 1-1 at Blundell Park, the Mariners were second best for most of the first half and went in a goal down at half-time after James Marwood opened the scoring.
A tough task appeared to have got more difficult when Scott Neilson was shown a straight red card but Town rallied and grabbed an unlikely equaliser through captain Craig Disley.
From then on, it was anybody’s game but Gateshead retained the edge and after Sam Hatton was also sent off for a second bookable offence, it was always going to be difficult for Town.
And so it proved, as Marwood struck again before substitute JJ O’Donnell hit a late third to send the Tynesiders to Wembley and condemn the Mariners to another season in non-league.
One change was made to the Town side from Thursday’s first leg, with Chris Doig coming in for the suspended Shaun Pearson.
Otherwise, it was as you were, with James McKeown in goal and Hatton, Doig, Andrew Boyce and Aswad Thomas lining up in defence.
Alex Rodman, Disley, Scott Kerr and Neilson were the midfielders, with Ross Hannah and Lenell John-Lewis picked as the strikers.
There was also one change on the bench, with Oumare Tounkara replacing Dayle Southwell. Andy Cook, Andi Thanoj, Paddy McLaughlin and Jamal Fyfield were also named as substitutes.
Gateshead boss Gary Mills made one alteration too, with Jamie Chandler coming into the midfield in place of Josh Walker, who dropped to the bench.
Town kicked off and they were the first to register a shot when John-Lewis fired wide from 20 yards on three minutes.
Neilson then forced home keeper Adam Bartlett into action a minute later with a low effort from a similar distance, which the stopper comfortably held.
As in the game at Blundell Park, Gateshead began the game looking to play patient, possession football and wait for openings, with Boyce having to make a timely interception to break one early attack down.
Chandler had a good chance for the home side on nine minutes when he shot from 15 yards but McKeown got down well to make an important save.
Town then began to come into the game more, having their own spells with the ball but without causing any real problems for the Gateshead backline.
A foul on Rodman on the right gave the Mariners a free kick in a promising position and Kerr’s ball came back to Neilson on the 18-yard line. His shot was deflected for the game’s first corner, which was cleared.
Gateshead took the lead on 22 minutes and it was a goalkeeping error which gifted them their advantages, as a 25-yard shot from MARWOOD looked comfortable for McKeown but slipped through his grasp and into the net.
Town responded with an overhead kick from John-Lewis being easily saved, before a free kick came for a foul on Thomas on the left but Kerr’s delivery was straight at Bartlett.
The hosts were on top though and they had another chance when Marcus Maddison hit a snap-shot from 25 yards but this time, McKeown got down to make the stop.
Disley was shown the first yellow card of the game on 33 minutes when he brought Maddison down after giving the ball away in midfield but the resulting free kick hit the Town wall.
Grimsby attacks were becoming rarer as Gateshead dominated, although a Hannah cross nine minutes before the break was volleyed back across goal before being cleared.
The Mariners were struggling to create anything against a home side who were now content to just keep the ball, knowing they were in pole position for a trip to Wembley.
Another home attack down the right looked promising but a flick over the top proved too far ahead of Maddison and the ball rolled out for a goal kick.
Thomas found the space to put a cross in from the Town left as the game moved into one added minute but no attackers were there to get on the end of it and Bartlett gathered.
The half ended with the visitors in possession but they were unable to create a chance and the referee’s whistle brought great applause from the home fans, who were now 45 minutes from the final.
Grimsby would have to force the issue in the second half and look for something different in order to keep their season alive.
No changes were made before the restart and John-Lewis had the first opportunity of the second half two minutes in when he held off his man on the edge of the box but hit a weak shot that went to Bartlett.
At the other end, Gateshead won a corner but nobody could connect with it and the ball went out for a Town throw-in.
Right-back Carl Magnay hit a shot well over the bar from outside the box on 50 minutes, before Doig had to concede a corner, which led to Kerr clearing off the line as the hosts looked set to make it 2-0.
Gateshead retained possession and won a free kick just outside the penalty area but Maddison’s shot cannoned back off the Town wall.
Town looked to have created an opportunity when a through-ball for Hannah was laid back for John-Lewis but he was crowded out by the home defence.
The game then took another turn when the Mariners were reduced to 10 men, as Neilson was shown a straight red card for following through with a poor challenge on the edge of the Gateshead box after a shot was blocked.
Town were almost back in the game in bizarre fashion as a clearance from Bartlett hit John-Lewis and spun back towards goal, only for it to hit the side-netting.
Boyce was booked for a trip inside his own half and from the free kick, the hosts thought they had settled the tie, as James Curtis powered a header home, only for it to be ruled out for offside.
Then, just before the hour, the Mariners equalised completely against the run of play, when a ball across the penalty area from Thomas was met by DISLEY and he shot into the roof of the net to make it 1-1.
Suddenly, the Mariners were back in it and they were now the team on the attack, as John-Lewis looked to place a shot from 20 yards but it was saved by Bartlett.
The first substitution saw O’Donnell replace Colin Larkin in the Gateshead attack on 67 minutes, with the home side still on top but beginning to make a few more mistakes in possession than they had in the first half.
Maddison had an opportunity after collecting a pass from John Oster and beating Thomas but he dragged his shot wide.
That proved to be the striker’s last chance as he was replaced by Liam Hatch soon afterwards.
Hatton was yellow-carded for a foul just inside the Gateshead half and a scare came for the Mariners when McKeown failed to claim a cross but the ball was cleared.
Chandler was the next name to go into the referee’s notebook for a foul on Thomas but Kerr’s free kick went through to Bartlett in the home goal.
Thomas did well to make ground down the left and win a throw near the corner flag as Town launched an attack but ultimately, it came to nothing.
And the Mariners were forced to play the last 11 minutes with just nine men, when Hatton was shown na second yellow card for a poor challenge near the halfway line.
John-Lewis was now leading the line on his own and a double substitution saw Fyfield and Thanoj come on for Hannah and Kerr.
It was now a tall order for the away side, although they were still level on the scoreboard.
That was not to be the case for very long though, as Gateshead made their numerical advantage count by grabbing what looked like it could be a decisive second goal.
Great vision from Oster saw him pick out MARWOOD and his curling shot beat McKeown and hit the top corner of the net.
Cook replaced Doig for the final five minutes, with Town now having to throw caution to the wind in a bid to force a second equaliser.
Five added minutes were signalled and a brilliant double save from McKeown kept the Mariners in the game for a little longer.
But the home side were to make sure of their place in the final in the last of the added minutes, when the keeper raced off his line but failed to intercept a through-ball, leaving O’DONNELL with the simple task of rolling the ball into the net to make it 3-1.
A premature pitch invasion from the home fans only prolonged the Grimsby agony for a little longer, before the joyful Tyneside supporters were back on the field at the final whistle to celebrate their team’s success.
For the Mariners, it is back to the drawing board once again after missing out on promotion through the play-offs for a second consecutive season.