Stevie Aitken, the Dumbarton manager, hailed his players as they all but clinched their place in the Championship for next season.
The spirited Sons thwarted Dundee United’s hopes of clinching second place with goals in either half from Robert Thomson and Lewis Vaughan after Tony Andreu’s 22nd minute headed opener for the Tannadice side. Thomas Mikkelsen hit a late equaliser for the hosts who were booed off at the end.
It means Aitken’s part-time side are now three points off rivals Raith Rovers with a nine-goal plus goal difference going into the final day when Dumbarton host Falkirk.
“It’s a proud day,” said Aitken. “Barring a disaster we’ll be safe. We knew we had to get at least a point to make sure from our last two games that we would be safe from the play-offs so I’m absolutely chuffed.
“We were tipped to get relegated before a ball was kicked but we’re good at proving people wrong.”
United got things under way knowing promotion rivals Falkirk had drawn 2-2 with Queen of the South and took the lead in 22 minutes. Blair Spittal’s corner was met at the near post by Andreu and his eight-yard header was too strong for visiting goalkeeper Alan Martin.
But Dumbarton equalised in 35 minutes. Ross McCrorie’s corner was helped on by Stuart Carswell and Thomson headed home from close-range.
Simon Murray almost restored United’s lead in 58 minutes when his curling shot crept just inches wide of Martin’s far post.
Dumbarton, though, went ahead in 65 minutes.
On-loan Hibs midfielder Sam Stanton cut out Willo Flood’s pass before setting free Vaughan and the on-loan Raith Rovers man calmly chipped the ball over the advancing Cammy Bell in the hosts’ goal.
United levelled in 79 minutes after substitute Ali Coote’s shot was parried by Martin and Mikkelsen tapped home the rebound.
Ray McKinnon, the United manager, was left nursing an overall sense of frustration.
“It was one that got away,” he said. “We would have won if we had shown a bit more quality in front of goal. We gifted them two goals but we just have to go to Morton next week and try to win. If we can do that then we’ll go into the play-offs as a real force.”
United lie third, a point behind Falkirk with a game to go. If they remain there they will face Morton the play-off quarter-finals.