Forfar will play League 1 football next season and Peterhead will return to Scotland’s fourth tier after three years away.
Two first-half goals from Lewis Milne and David Cox gave Peterhead a mountain to climb and Danny Denholm’s second-half goal ended the game as a contest.
Peterhead made four changes from the first-leg as Scott Ross, Nicky Riley, Simon and Leighton McIntosh were in for Craig Reid, Jordon Brown, Grant Anderson and the suspended Rory McAllister.
Forfar made just one change as Jim Lister came in for the injured Gavin Swankie.
Forfar made the perfect start as Lewis Milne scored from Jamie Bain’s throw-in, capitalising on some slack defending within the first five minutes to give Forfar an early advantage.
Scott Brown shot the ball well over the bar from 20 yards out after some link up play by the Blue Toon.
Martyn Fotheringham should have made it two for Forfar after a header into the box by Eddie Malone fell to his feet and hit it over the bar from six yards.
Some poor defending from Peterhead gave David Cox the ball six-yards from goal and he coolly slotted it home, making it 4-1 on aggregate for Forfar and leaving the Blue Toon with an uphill struggle.
Michael McMullin appeared to be fouled as he was brought down just outside the box, but referee Gavin Duncan didn’t call it.
Good interplay between Stevenson and McIntosh gave the striker some space the his effort flashed across the goal.
McIntosh took a shot that was saved by Forfar keeper Adam, but ball fell to Riley who fired it into the side netting.
Forar had to make a change after Fotheringham was injured and was replaced by Aiden Malone.
After going two goals down, Peterhead controlled possession but clearly missed Rory McAllister as they were unable to find the net.
Forfar put the home side under pressure in the last five minutes of the first-half with a couple of corners that Toon keeper Graeme Smith struggled to get a hold of, but there was enough Peterhead players in the box to prevent the ball going in.
Forfar made the perfect start in the second-hald too as Danny Denholm found himself in space in the box after, hitting the ball with the outside of his foot and finding the net.
Denholm’s goal made it 5-1 on aggregate and looking too far for Peterhead to salvage a positive result.
Scott Brown took a shot from distance and it went narrowly wide.
The misery continued for Peterhead as Aiden Malone back-heeled the ball into the net, leaving Peterhead needing five goals to even make it to extra-time.
Peterhead got a consolation goal when Scott Brown took a shot from distance that went into the bottom-corner of Forfar’s goal.
Josh Peters got a fifth for Forfar in the last 10 minutes as Jim Lister squared the ball to him in the box.
Forfar won 7-2 on aggregate as and away support invaded the pitch to celebrate their promotion into League 1 next season.