Chesterfield took the lead through Sam Morsy but a streetwise Millwall quicky drew level before winning the game 2-1 with an early second half Lee Gregory goal.
After a strong Spireites opening, captain Morsy drilled home a beauty of a strike from 30 yards 25 minutes in, however the deserved lead lasted ony 90 seconds and Millwall drew level thanks to a smart Aiden O'Brien header.
From the off in the second half Millwall took the lead, Gregory was sharp and quick and sliced though the home defence before sliding home a neat finish.
It was a confident start from both sides but it was the visitors who had the game’s first chance in a contest which was set to have a fiery atmosphere from the start. Gregory burst forward and found Jed Wallace on the edge of the box, but his powerful effort was gathered at the second time of asking by Tommy Lee.
Soon after, Steve Morison put a deflected strike onto the roof of the net as the Lions looked to get a hold on the contest. However at the other end, a Jay O’Shea corner found Sam Hird at the far post, but he couldn’t keep is header down.
There was a great atmosphere in the ground, particularly from the Spireites fans, and they were almost celebrating a goal with 13 minutes gone; captain Sam Morsy lined up a fierce drive from 25 yards out but it flew narrowly wide.
Chesterfield were beginning to stretch the away side’s defence, first with Dion Donohue volleying straight at Lions 'keeper Jordan Archer, before Lee Novak’s cross was diverted wide by Sylvan Ebanks-Blake.
Despite the game turning into somewhat of a flat affair, Novak thought he had put his side in the lead when put through by a superb Ebanks-Blake pass, but he could only find the side netting.
Yet the Spireites didn’t have to wait long to find the net. O’Shea found Morsy in space, and he fired an unstoppable strike past Archer into the corner for his first goal since September.
After a short spell of pressure on the edge of the box Millwall rallied and came up with an instant reply, a cross found Aiden O’Brien who headed into the top corner to level things up.
The game re-found its spark with things heating up on the pitch. Next to go close was the impressive O’Shea whose powerful volley from inside the area was collected by Archer.
As the game headed towards half time Chesterfield were the side in the ascendency. Charlie Raglan went down the area under a Jimmy Abdou challenge, but the referee waved away the Spireites’ appeals.
The second half had barely begun when Millwall completed their comeback. Wallace and Morison broke through the middle to find Gregory, and the former Halifax Town man slotted past Lee from 12 yards.
The goal shocked Chesterfield as Millwall grabbed the game by the scruff of the neck. They almost made it 3-1 seconds later after an almighty scramble on the goal line, but Chesterfield eventually cleared their lines.
With an hour gone the Spireites were fighting to stay in the game, both sides playing end-to-end stuff. While Chesterfield were creating a long line of half-chances, Millwall were looking dangerous on the break.
Gboly Ariyibi shot wide from a difficult position, while at the other end some neat play between Wallace and Abdou led to the former firing over.
Chesterfield were battling to rescue something from the game, and Morsy almost eqaulised when he unleashed another powerful effort which slipped through Archer’s hands, but stopped inches from the line.
The pressure was increasing on the Millwall goal, this time Gardner firing across the face, before Byron Harrison forced a super save from Archer when he sent a glancing header towards the near post.
The Lions almost put the game to bed at the other end when Morison picked the ball up on the left and cut inside. His ball across the face was deflected goalwards, before being tipped onto the bar by Lee and then cleared to safety.
In the dying minutes Chesterfield were throwing everything at Millwall in the hope of salvaging a point, first with a low Gardner cross being cleared before substitute Mani Dieseruvwe hooked a shot wide.
The home side were camped on the edge of their opponent’s box for the final few minutes but they couldn’t muster the goal they required as Millwall claimed all three points.
Chesterfield: Lee (gk) - Talbot (Dieseruvwe 87'), Hird, Raglan, O'Neil - Morsy (c), Donohue, O'Shea, Ariyibi (Gardner 65') - Novak, Ebanks-Blake (Harrison 72')
Subs not used: Chapman (gk), Humphreys, Onovwigun, Simons
Millwall: Archer (gk) - Cummings, Williams, Gregory (Onyedinma 88'), Beevers, Webster, Ferguson (Martin 76'), Morison, O'Brien (Upson 78'), Wallace, Abdou
Subs not used: Forde (gk), Marquis, Nelson, Thompson
Chesterfield: Morsy 25'
Millwalll: O'Brien 27', Gregory 47'
Attendance: 7,078 (854 away fans)