Only once this season have the Stags come back from going a goal behind to gain anything, and so it proved again.
The home side rallied well after Richie Foran's 30th minute spot kick, but the Quakers always looked in control.
Town almost found a way through in the opening stages, Jake Buxton, John Mullins and then Simon Brown all seeing headers saved keeper David Stockdale.
Despite the early chances, the Stags were penned back for long periods by the Quakers' quick passing and physical presence.
A fine passing move between Neil Austin and Julian Joachim ended with Mickey Cummins' shot tipped over by keeper Carl Muggleton.
Muggleton then miscued a punch from a Paul Mayo corner, only for Richie Foran to mishit his shot straight back to the stranded keeper.
However the north-east side eventually took the lead thanks to a controversial penalty on the half hour.
Dan Martin was penalised for pulling back Ian Miller at a Mayo corner, despite no appeals from the Quakers' players, and on-loan striker Richie Foran drilled his spot-kick into the bottom corner.
A break away could have doubled Darlington's lead on half-time, but Foran's first-time low drive was beaten away by Muggleton.
The save could have proved vital in first half injury time when Stephen Dawson burst clear into the area, only to lift his effort high and wide.
Mansfield continued to press for a leveller at the start of the second half, but the best chance fell at the other end to Foran whose shot from the edge of the box skimmed the bar.
Darlington defender Foster was lucky to escape with a yellow card after hauling down Michael Boulding as he raced clear in the 62nd minute.
For all their pressure, however, the Stags failed to force Stockdale into a save.
The Quakers should have made the game safe. Substitute Clarke Keltie's deft lob was tipped over by Muggleton and Foran went close three times to securing victory.