On-the-whistle report: AFC Wimbledon 1 Rotherham United 2
Record signing Freddie Ladapo scored a debut goal to put the Millers in front and an 84th-minute intervention from Clark Robertson secured all three points after a Don equaliser.
The visitors were in complete control at the break following the Ladapo's 29th-minute opener but were pegged back early in the second half by a Joe Pigott header.
With time running out and both sides looking capable of scoring, Robertson screwed a low shot into the corner of the net to spark wild scenes in the sold-out away stand.
It was the first time Rotherham have won on the first day of the season since 2012.
Ladapo opened his account just before the half-hour mark, striking from close range when Michael Smith's header from Joe Mattock's corner had fallen to him.
It should have been the second goal of the £400,000 forward's Rotherham career because it had taken point-blank heroics from Wimbledon goalkeeper Nik Tzanev to deny him on nine minutes following dangerman Kyle Vassell's cross.
The home side had no answer to the Millers' three-pronged attack and Vassell's running caused trouble down both flanks.
His 14th-minute cross from the left deserved a better finish than Michael Smith's wayward header.
Daniel Iversen didn't have a save to make in the visitors' goal in the opening period and it took the Dons seconds before the break to pose a threat, Callum Reilly shooting narrowly off target from the edge of the area.
Having been totally outplayed in the first half, Wimbledon needed only five minutes of the second to equalise as Pigott headed home unchallenged from a corner.
Rotherham came close to falling behind eight minutes later when Anthony Hartigan poked inches wide.
They weathered the pressure and it needed an unbelievable goalline clearance to prevent Ladapo adding to his total on 68 minutes after Matt Crooks had chosen to play in his teammate rather than shoot himself.
Soon after, Crooks freed Smith on the right but the big attacker fired his shot harmlessly across the goal.
Substitute Ben Wiles tested Tzanev with a 20-yard volley in the 79th minute while Will Nightingale wasn't far away with a header at the other end.
Then came Robertson's decisive intervention. And the celebration.
Goals: Ladapo 29, Robertson 84 (Rotherham); Pigott 50 (Wimbledon).
Wimbledon (4-4-2): Nik Tzanev; Luke O'Neill, Terrell Thomas (Kwesi Appiah 85), Paul Kalambayi, Rod McDonald; Nesta Guinness-Walker, Anthony Hartigan (Shane McLoughlin 80), Will Nightingale, Callum Reilly; Michael Folivi (Dylan Connolly 83), Joe Pigott. Subs not used: Joe McDonnell, Scott Wagstaff, Mitchell Pinnock, Jack Rudoni.
Rotherham (4-3-3): Daniel Iversen; Matthew Olosunde, Michael Ihiekwe, Clark Robertson, Joe Mattock; Shaun MacDonald, Daniel Barlaser (Ben Wiles 69), Matt Crooks; Freddie Ladapo (Jamie Proctor 84), Kyle Vassell (Carlton Morris 75), Michael Smith. Subs not used: Lewis Price, Richard Wood, Jamie Lindsay, Jake Cooper.
Referee: Brett Huxtable (Devon).
Attendance: 4,657 (785).