Visitors Mansfield, who are still struggling for points, took full advantage in a second half where they dominated the game totally.
The lowly visitors began the game strongly and in the ninth minute top scorer Michael Boulding looked certain to score but was denied by Darlington keeper David Stockdale.
Soon afterwards Stockdale was called into action again when he punched clear a menacing cross from Jefferson Louis that fell into the path of Boulding. Darlo captain Steve Foster slid in to deny the Mansfield striker a shot at goal.
In the 16th minute Louis should have scored but failed to connect cleanly with the ball after being set up by Johnny Mullins. Darlington's frustrations were clear when top scorer Tommy Wright was booked in the 19th minute for a deliberate handball.
But the early nerves were forgotten in the 22nd minute when the home side took the lead. A Julian Joachim shot was deflected for a corner and when the kick was sent in by Bryan Hodge, defender Neil Austin slid in at the far post to turn the ball over the line.
The game evened out with neither side creating many more chances as the game headed towards the half-time interval. But in the dying seconds of the half Louis fell to the ground and referee Neil Swarbrick consulted his linesman before showing Darlington defender Alan White a straight red card.
In the second half the visitors made their advantage count and in the 56th minute Matt Hamshaw sent over a right-wing cross for Louis who stooped to head the ball past Stockdale for the equaliser.
Darlington panicked and the visitors took full advantage.
In the 65th minute another header from Louis found Stephen Dawson in space and he ran into the area before coolly firing under Stockdale and into the bottom corner of the net, to give the visitors not only the lead, but a valuable three points in their battle to avoid relegation.