James Norwood struck his 32nd goal of the season to help take Tranmere to Wembley for the Sky Bet League Two play-off final against Newport.
A header from Forest Green skipper Joseph Mills after just 13 minutes cancelled out Ollie Banks' cracker from the first leg.
However it was Norwood's goal after 27 minutes which proved decisive, earning a 1-1 draw on the night and a 2-1 victory on aggregate, while the hosts had Carl Winchester sent off midway through the second half.
Tranmere had started the better at The New Lawn and chalked up the first shot of the game when Liam Ridehalgh tried his luck from outside the area but it was easily gathered by Forest Green keeper Lewis Ward.
The hosts soon got into their stride and opened the scoring when Junior Mondal floated a free-kick into the area which was met by Mills and his header ended up in the back of the net.
With the tricky Reece Brown causing problems for the visitors, Forest Green pushed for a second to give them the aggregate lead but struggled to find a way past impressive defender Manny Monthe.
At the other end, Banks fired a low effort at Ward before the visitors levelled on the night through a well-worked effort.
David Perkins sent a cross to the far side of the area where Kieron Morris was on hand to head down for star striker Norwood to crash a volley into the bottom corner.
The Gloucestershire side looked to hit back before the break but a Dayle Grubb snap shot was directed straight at the keeper while Ridehalgh pulled off a vital defensive header to deny Christian Doidge just before the break.
Forest Green boss Mark Cooper made a change at the break, replacing Mondal with George Williams as his side looked for the goal that would take the tie to extra time.
But it was the visitors who almost added to the scoreline two minutes after the restart when a deft Morris free-kick was only just missed by Sid Nelson six yards out.
Williams forced Scott Davies into a save at his near post and Doidge just missed out again when Liam Shephard's cross was gathered by the keeper.
Winchester also fizzed a shot low past the upright as Forest Green looked for their all-important second goal, but that was to prove his final input as he picked up a second yellow after 67 minutes for a foul on Norwood and, just like at Prenton Park, Cooper's side were reduced to 10 men.
There was one last effort from the home side two minutes from the end but Williams' free-kick into the area was scuffed wide of the target by Mills.
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