David Wheeler's goal two minutes into the game secured MK Dons an immediate return to League 1.
In a winner-takes-all match at Stadium MK, Dons were 1-0 winners over promotion rivals Mansfield, but Wheeler's header was enough to see Dons snatch it.
Paul Tisdale named as strong a team as he could for the occasion, making three changes to the side which started against Colchester. Joe Walsh and George Williams were back in defence as Dons played a back three for the first time since February, while Chuks Aneke returned up front as Ryan Harley, Jake Hesketh and Ouss Cisse were on the bench.
The stakes were simple: win the game and get promoted, and with that in mind, Dons flew out of the blocks and took the lead after just two minutes when David Wheeler headed home his third goal in four games to put Dons into pole position.
The game was on such a knife edge that the goal really did quite little to change the overall complexion of the day, though the weather changed almost minute by minute. Mansfield began to find their feet, but it was Dons who came closest to doubling the lead when Chuks Aneke saw his low effort cleared off the line after Kieran Agard picked him out on the edge of the six yard box.
With Mansfield having to ride the tide, David Flitcroft made two changes before half time. While Matt Preston's withdrawal was forced through injury, Willem Tomlinson was removed with tactics in mind, replaced by Danny Rose seven minutes before the break, in a bid to bring the visitors into the affair.
Predictably, Mansfield came out for the second half a completely different entity. Fast moving through midfield, Tyler Walker was their main outlet and looked to get in behind the Dons back line, but his final ball twice let him down as he sought to pick out CJ Hamilton.
Aneke though had the best chance to add to the scoreboard, this time seeing his strike deflected into the outside of the net.
They should have put the game to bed with 25 minutes to go though. Having his every move marshalled by the brilliant Krystian Pearce, Aneke finally beat the defender to tee up Agard one-on-one with keeper Conrad Logan, but the keeper did well to get a something on it to deny Dons a second.
Time was always ebbing away from Mansfield though, and with no real concrete chances for the visitors, Dons held on to claim promotion.
Referee: Lee Probert
Attendance: 20,718 (5,227)
MK Dons: Nicholls, Martin, Walsh, Williams, Lewington, Brittain, McGrandles, Houghton, Wheeler (Watson 69), Aneke (Simpson 90), Agard
Subs not used: Moore, Cisse, Hesketh, D'Ath, Harley
Mansfield Town: Logan, Benning (Grant 69), Preston (Turner 19), Bishop, MacDonald, Mellis, Tomlinson (Rose 37), Sweeney, Walker, Hamilton
Subs not used: Smith, Atkinson, Jones, Smith