A first-half strike by Adam Murray secured Mansfield's first home win in five games and left the Iron with just two points from their four festive games.
Despite dominating the last hour Scunthorpe forced just two saves from home keeper Kevin Pilkington - and only three fine late stops by his opposite number Paul Musselwhite denied Mansfield a more emphatic victory in a thrilling finish.
Musselwhite was left floundering in the 19th minute as Mansfield turned their early superiority into a goal. Wayne Corden pulled the ball back from the left wing and Murray's 20-yard drive swerved into the bottom corner past the diving keeper.
Two minutes later Corden flashed a 25-yard drive into the side-netting and then Colin Larkin also shot wide as the home side threatened to run riot.
In the 32nd minute, on a rare counter-attack, Scunthorpe should have levelled, the unmarked Michael Rankine scuffing his shot from Peter Beagrie's clever knockdown.
The chance sparked the visitors into life and Paul Hayes then blasted over from an acute angle after a quick turn.
The Iron continued to dominate at the start of the second half, Pilkington's fingertips stopping Rankine's close-range header.
In the 58th minute former Stag Ian Baraclough curled a 25-yard free-kick narrowly wide.
Two minutes later Rankine drove past the post after wriggling clear of his marker as Mansfield were forced to defend in depth.
Beagrie curled a long-range effort past the upright and then, eight minutes from time, Cliff Byrne's close-range header was well held by the diving Pilkington - Scunthorpe's last chance to rescue a point.
30 seconds later Mansfield wasted a chance to make it 2-0 when Corden released Simon Brown only for the home debutante to shoot straight at the keeper.
Moments later Murray's piledriver through a crowded penalty area was well held by the diving Musselwhite.
And in stoppage time Musselwhite again kept Scunthorpe in the game, beating away a fierce shot from Brown.