After a goalless first half, the away side found an extra gear in the second period, as goals from Josh Morris, Kevin van Veen and then Sam Mantom secured a terrific win on the road.
The Iron made four changes heading into the match. Luke Daniels returned in goal in place of Joe Anyon, while Levi Sutton took the place of Scott Wiseman.
Elsewhere, Duane Holmes came in for Sam Mantom, with van Veen taking the place of Tom Hopper.
The visitors had the home side on the back foot early on, with a cleverly-worked corner kick almost resulting in Sutton testing Ryan Fulton in the Chesterfield goal. His defence in front of him did well though, and blocked the shot.
Chances continued to present themselves, as Morris curled a long range free kick marginally over the crossbar with 11 minutes on the clock.
Holmes was next to see the whites of the Spireites’ shotstopper’s eyes when he rose highest in the area. However his close range header was just a little too close to Fulton, who gathered comfortably.
Daniels was then drawn into his first save of the afternoon with Ched Evans hitting a rasping effort towards goal. The Scunthorpe ‘keeper wasn’t troubled though, as he held on.
Some great play on the half an hour mark from Madden and Dawson almost then led to the opener. After Madden held the ball up, he played it square to Dawson, who in turn teed up Morris on the edge of the box, but the winger pulled his strike just wide of the goal.
Right on the strike of the break though, Madden had the game’s best opportunity up until that point when he went through one on one with Fulton. The Scot spread himself well and denied the Iron frontman however, who couldn’t quite squeeze the ball underneath the opposing ‘keeper.
That chance would be the last of a half which Graham Alexander would have felt his side had the better of, as they walked off the field at the interval.
United began the second period in the same manner as they did the first. Morris had the first chance after the restart with a sliced effort following a good knock-down from van Veen.
Five minutes into the half, Alexander’s side did get their deserved lead. The delivery from the left from the boot of Morris was brilliant - so perfect that it evaded everyone and ended up in the back of the net, to send the winger onto 14 goals in all competitions for the season.
The opener was soon backed up by a superb second from van Veen. Holmes’ marvellous run from inside his own half couldn’t be matched by anyone in blue, with the American then feeding the Dutchman, who drove the ball under Fulton and into the back of the net.
The away side could have added to their two goal lead when Madden broke the offside trap with 12 minutes left on the clock. His outstretched boot couldn’t quite poke the ball past Fulton though, whose sprawling save did enough to foil the Iron frontman.
That third wasn’t long in coming though, as substitute Mantom put the finishing touches to a fine display on 85 minutes. You could argue it was the pick of the bunch too, as an exquisite cross-field pass from van Veen was calmly dispatched into the bottom corner by the ex-Walsall midfielder.
Opportunities for a fourth came for Alexander’s men, but they had to make do with three goals and three points, as they extended their lead at the top of the League One table.
Chesterfield: Fulton, Hird, Liddle, Evans, O’Neil (Simons, 82), Nolan, Donohue, Anderson, O’Shea (Mitchell, 70), Ariyibi, German (Gardner, 61).
Substitutes not used: Evatt, Dimaio, Allinson, Graham.
Scunthorpe United: Daniels, Wallace, Mirfin, Dawson (Smallwood, 80), Madden, van Veen, Morris (Goode, 86), Bishop, Holmes (Mantom, 73), Townsend, Sutton.
Substitutes not used: Anyon, Hopper, Margetts, Ness.
Attendance: 6,328 (1,152 away).