The first half was goalless, during which both sides were forced to make a substitution after both Michael Reddy and Craig Armstrong were injured in an aerial challenge.
[1] Grimsby had been denied automatic promotion on the final day of the regular season when they conceded a last-minute equaliser to Northampton Town while Leyton Orient scored a late winner at Oxford United.
The visitors took the lead two minutes before half-time when John Finnigan scored from Shane Duff's knockdown.
The game ended goalless, with Guinan shooting over the Wycombe crossbar from close range in the 70th minute.
Midway through the first half, Gary Jones put Grimsby into the lead from a Curtis Woodhouse cross.
[9] In the two league games between the clubs during the regular season, Grimsby won both encounters: a 3–0 win at Whaddon Road in October 2005 was followed by a 1–0 victory at Blundell Park in April 2006.
[13] Grimsby's Jones was selected in the starting eleven after a successful appeal overturned the red card he received in the second leg of the semi-final.
Three minutes later, a mistake from Jones allowed Guinan to shoot, but his strike was straight at Mildenhall; Woodhouse's shot then cleared the Grimsby crossbar by some distance.
In the 17th minute, Finnigan's attempt went wide before an aerial collision between Craig Armstrong and Reddy forced both players to be substituted, Mickey Bell coming for Cheltenham and Gary Cohen for Grimsby.
In the last minute of the first half, Shane Higgs saved a low shot from Cohen before Parkinson's strike went over the crossbar.
Higgs then saved a diving header from Jones in the 80th minute before Spencer was shown a yellow card for a foul on Mildenhall.
Grimsby's Junior Mendes then came on for Marc Goodfellow before Woodhouse was shown the match's second yellow card, for a foul on Spencer.
After five minutes of stoppage time, the referee blew the final whistle with Cheltenham securing a 1–0 victory and promotion to League One.
[13] However, he admitted that "To be fair we possibly did not deserve it on the day ... Cheltenham started tremendously well but we didn't get into the game until the 30th minute.