Three splendid goals from James Henry and Steve Morison (2) sent The Lions up to 11th in the Championship as Kenny Jackett's men laid to rest the ghost of the 2009 Play-Off final.
The heartbreak of that Wembley defeat by Scunthorpe United 18 months ago still rankled. So much so infact, that Den chairman John Berylson insisted on flying back to America before today's game following a whirlwind 48 hour trip to London. The reason? He had never seen The Lions beat Scunny in five previous attempts and wanted to see if his absence would bring the desired change in fortune!
And he wasn't disappointed; Henry set the ball rolling with the first on 23 minutes, with classy finishes from Morison on 81 and 86 minutes securing Millwall's first victory against The Iron in six attempts.
It was mission accomplished for boss Jackett, who was delighted with the three-point haul and a third consecutive clean sheet..
"I felt that we had a number of chances and was delighted that we took them today," he enthused.
"They were all excellent goals, but the first one from James Henry was crucial.
I must admit that I was still nervous at 1-0, but we managed to keep it tight and competitive and Steve Morison's two late strikes made sure of a very good win."
Jackett made just one change to the side that started at Preston with, as expected, Jimmy Abdou replacing Liam Trotter (hamstring) in midfield alongside Tamika Mkandawire.
After a quiet opening quarter of an hour, the game sprung into life when first Scott Barron was sent sprawling in the danger zone after Morison slipped the ball through to him, but referee Booth waved play on.
Morison and then Henry fired narrowly wide as The Lions began to pressurise the visiting rearguard.
The breakthrough finally came on 23 minutes when Henry picked up the ball in a central position and set off on a powerful forward run before unleashing an unstoppable drive into the bottom left hand corner, giving keeper Joe Murphy no chance.
Calvin Andrew was agonisingly close to marking his home debut with a goal two minutes before the break, but fractionally mistimed his jump and placed a header over the bar from Morison's delivery barely three yards out.
Lions fans got their first look at new signing Josh McQuoid when he came on at the start of the second-half in place of Andrew.
Mkandawire had already sent a glancing header from Jason Puncheon's corner narrowly wide before McQuoid was a whisker away from marking his debut in style, but his free header from Morison's pinpoint delivery flew wide.
Alan Dunne lashed into the side netting following more good work by Puncheon, while at the other end it took an exceptional piece of defensive play by Danny Shittu to avert the danger from sub Garry Thompson, after the Iron man had burst forward, with the linesman's flag surprisingly not raised for offside.
With Scunthorpe sensing that The Lions were getting a little jittery, Morison settled those nerves with two emphatic finishes.
The first came with nine minutes remaining when he powered down the left and from virtually the bye-line spotted the tiniest of gaps in the goal. It looked to be an impossible angle, but Morison fired the ball home like threading through the eye of a needle to put The Lions 2-0 ahead.
Morison's second - and Millwall's third - followed on 86 minutes with an instinctive finish, controlling the ball 18 yards out and lashing home past the unsighted Murphy to wrap up victory in style.
Millwall: Forde, Dunne, Barron, Abdou, Robinson, Shittu, Puncheon (Schofield, 88mins), Mkandawire, Morison, Andrew (McQuoid, 46mins), Henry. Subs not used: Mildenhall, Craig, Harris, Ward, Hackett.
Scorers: Henry (23mins), Morison (81, 86mins)
Scunthorpe United: Murphy, Wright, Byrne, Jones, Nolan, Wright (MacDonald, 78mins), O'Connor (Forte, 59mins), Togwell, Dagnall, Woolford, Sears (Thompson, 59mins). Subs not used: Slocombe, McClenahan, Godden, N'Guessan.
Ref: RJ Booth
Att: 8,937 (away 162)