The Mariners finished off the job they started with the 3-0 semi-final first leg victory at Blundell Park with a professional performance in the second leg in Kent.
Dartford started brightly and could have reduced their deficit on several occasions in the first half but Town held firm to leave themselves on the brink of a trip to the national stadium.
After the break, Grimsby had chances make absolutely certain of their final appearance but could not force a breakthrough on the day.
In the end though, it did not matter, as the Dartford challenge faded and the Mariners were able to celebrate with their travelling supporters and begin making plans for the final against Wrexham on March 24.
Three changes were made to the Town side that slipped to the club’s first defeat since November at Braintree in midweek.
Out went Aswad Thomas, Marcus Marshall and Andy Cook, with Bradley Wood, Jamie Devitt and Richard Brodie coming into the starting XI.
That meant Lennell John-Lewis continued in attack after impressing on his first start for the club against the Essex side.
James McKeown started in goal, with Sam Hatton, Shaun Pearson, Ian Miller and Wood forming the defence.
Joe Colbeck began on the right of midfield, as Craig Disley and Derek Niven continued their partnership in the middle and Devitt slotted in on the left.
Brodie and John-Lewis were the strikers, which meant Ross Hannah again had to settle for a place on the bench, alongside Frankie Artus, Cook, Thomas and Marshall.
Dartford were without Lee Noble, who was sent off in the closing stages of the first leg at Blundell Park last week, while Jacob Erskine came into Tony Burman’s side in attack.
The home side had the first chance of the game when a cross from Ryan Hayes had to be put behind by Wood for a corner, which was headed away by Pearson.
At the other end, a cross from Colbeck almost caught home keeper Marcus Bettinelli out but the stopper managed to gather the ball underneath his crossbar without it crossing the goal-line.
A free kick for Dartford soon afterwards provided another good chance but Elliot Bradbrook could only power a free header straight at McKeown.
Two more Dartford corners followed around the ten-minute mark as the hosts looked for the early goal that would bring the tie back to life as a contest but nothing came of them, despite appeals for a penalty for a handball against Hatton.
The first Town corner came on 12 minutes but Devitt’s delivery from the left was cleared.
Another Mariners corner, this time from Colbeck on the right, led to John-Lewis heading wide.
The game was moving from end to end and Lee Burns was the next to have a chance for Dartford, although his shot was saved by McKeown in the Town goal.
Grimsby looked to launch a break when a mistake by defender Tom Champion allowed Brodie to bring the ball clear but Champion recovered well, before he was fouled by Brodie.
A Town free kick from Colbeck was won by Pearson on 18 minutes but a free kick was given against John-Lewis for dangerous play as he attempted an overhead kick.
Another Dartford corner taken by Hayes was dealt with by the Town defence as the 20-minute mark passed with the away side’s three-goal first leg lead still intact.
Colbeck hit a shot well wide at the midway point of the half but the home side, as expected, were asking most of the attacking questions and an effort by Bradbrook was blocked for a corner by Hatton after a free kick given away by Brodie.
Town were still creating chances though and John-Lewis headed wide after a cross from Colbeck on 28 minutes.
A free kick for a foul on Brodie was chipped in by Hatton but keeper Bettinelli gathered the ball at the second attempt.
The Mariners created a good opening when Disley found Colbeck and his shot was saved by Bettinelli, only for the offside flag to go up against John-Lewis as he looked to get onto the rebound.
Brodie won a corner on the right with seven minutes of the half to go but Colbeck could only find the arms of Bettinelli from the flag.
Town won a free kick inside the Dartford half on 42 minutes but Hatton’s delivery was too strong for Pearson and the ball went through for a goal kick.
The Mariners were having more possession as the half drew towards its conclusion and John-Lewis sliced a cross over the bar, before good work by Devitt almost led to a chance inside the penalty area.
Two added minutes were played at the end of the half and with no further chances for either side, it remained goalless at the break.
Dartford had started brightly but Town ensured they retained their three-goal cushion from the first leg and were still in full control of the tie with 45 minutes to go.
No changes were made at the interval and Grimsby had the first opportunity of the second half, as Devitt forced Bettinelli into making a good save to tip his shot away for a corner.
The Mariners were looking for the goal that would put the tie to bed and they almost had it with a prod from John-Lewis on 48 minutes but again, Bettinelli was there to make the stop.
Another chance came soon afterwards, with a run by Devitt getting him into the box but after he found Brodie, the striker could not profit.
Devitt was the main threat and he fired a cross-shot on 50 minutes that was almost touched into the net by John-Lewis, although the offside flag went up against the striker.
Dartford’s first chance of the second half came when a long throw into the box fell for Erskine but he mis-kicked in front of goal and the ball eventually found its way out for a throw-in.
Miller had to make a good challenge after the ball broke free when a shot by Danny Harris was blocked but the defender got to it ahead of Erskine.
The resulting corner was not dealt with by McKeown and Town struggled to get it clear but striker Harry Crawford could not force the ball into the net and instead, hit it wide for a goal kick.
Another Dartford corner came on the hour but Pearson and Colbeck combined to clear it after Hayes’ delivery.
John-Lewis went close on 62 minutes, after he collected Hatton’s pass and beat defender Tom Bonner but hit a powerful drive just over the bar.
A good chance came at the other end soon afterwards, when a cross from Hayes was met by Harris but his header flew wide.
Colbeck tried a 30-yard shot on 66 minutes and the ball bounced in front of Bettinelli but the keeper was able to make the stop.
Marshall replaced Devitt with 20 minutes to go and his first involvement was to set off on a run before crossing for Brodie to head wide.
Cook was the next to come off the bench as he replaced John-Lewis up front for Town with a little more than 15 minutes to go.
A flashpoint came when Brodie and defender Adam Green were involved in an altercation, with both men receiving yellow cards.
That proved to be Brodie’s last involvement in the game, as he was replaced by Hannah for the last ten minutes of the game at the same time as Dartford also made a double substitution.
The travelling Town supporters were now beginning the countdown to Wembley, as the Dartford challenge appeared to have run out of time.
Five additional minutes were played at the end of the game and the Mariners were able to see it out, ensuring a clean sheet bonus to complete a job well done.
The Town players celebrated with their supporters, who will surely travel in big numbers for the final against Wrexham.
But the immediate focus for Rob Scott, Paul Hurst and their squad will be getting back on track in the Blue Square Bet Premier when they face Ebbsfleet United at Blundell Park on Tuesday.