Full-time score from Ewood Park
Danny Shittu headed the decisive goal to book Millwall an FA Cup Semi Final date with Wigan at the expense of Blackburn Rovers in Wednesday night's Quarter Final replay.
Defender Shittu was on hand to meet Chris Taylor's 42nd-minute corner and plant a firm header beyond the reach of Jake Kean in the Blackburn goal.
Whilst Shittu's head proved vital, so too did the outstretched leg of fellow defender Shane Lowry, whose exceptional goalline clearance in the second half denied Rovers a certain equaliser.
This might not have been the prettiest of games on a bumpy Ewood Park pitch, but at the end of the night that really didn't matter as the final whistle was met by scenes of sheer jubilation amongst the Millwall players and 574 visiting supporters.
"We're delighted to win," beamed assistant boss Joe Gallen. "I know it means we get through to the Semi Final but we haven't been winning many games and we didn't concede again which is good.
Blackburn have some good players but there weren't many clear cut opportunities against us.
The back four, plus Jack Smith and David Forde, if you look at them as a six, were outstanding in both games."
Smith, who returned to the starting line up in a midfield role when the teams met on Sunday, produced another excellent performance in the midfield and the whole team did in terms of effort and endeavour too.
Lions boss Kenny Jackett named an unchanged team and his side again looked compact, organised and well-disciplined against a Rovers side yet to concede a goal in the FA Cup this season.
In the opening three minutes Leon Best stung the hands of David Forde with a shot that the Lions keeper held low to his right just seconds after Andy Keogh floated a header from Shane Lowry's deep cross wide of the mark as the teams exchanged early chances.
Another long range shot from Best on the quarter hour was deflected for the first corner of the game and when a short delivery was played top David Dunn, the midfielder's sweetly struck effort curled a whisker wide of the post.
Chris Taylor worked an opening with some deft footwork after 24 minutes and went for goal from 20 yards, but his rasping drive flashed wide of Jake Kean's goal.
With both defences in dominant form, scoring opportunities were pretty restricted to shots from distance with Taylor twice firing over from near-identical positions as The Lions tried to find a way through.
However cometh the moment, cometh the man and it was the man-mountain that is skipper Shittu who broke the deadlock three minutes before the break.
The irrepressible Taylor delivered an inch-perfect corner and there was Shittu to send a textbook header past Kean and into the back of the net.
Such was his delight, Shittu ripped his shirt off and was promptly booked by referee Mark Clattenburg, leaving the Lions defender walking a second-half tightrope.
But there were thankfully to be no further cards brandished Shittu's way as the skipper and his team-mates dug in to see out a nervy second period.
On the rare occasion that Blackburn did breach the visiting rearguard,
Lowry produced a great block from Josh King's goalbound shot after Scott Dann headed Pedersen's 49th-minute corner across goal. Pedersen then wasted a promising free-kick position firing wildly off target as frustrations among the home faithful grew.
But it took a superb goalline clearance from Lowry to avert the danger after Best's mazy run and shot so nearly produced an equaliser.
Rovers tried to build up a head of steam but simply ran out of ideas, and noticably belief, as Millwall's grew with every passing minute.
In fact Taylor could have added a second goal for Millwall right at the death, but blazed wastefully over following great work by sub John Marquis.
Blackburn Rovers: Kean, Olsson, Lowe, Dunn, Best, Rhodes, Pederson, Olsson (Gomes,, King (Forrester, 76mins), Dann, Hanley. Subs not used: Sandomierski, Givet, Rekik, Goodwillie, O'Sullivan.
Booking: Dunn (44mins)
Millwall: Forde, Dunne, Lowry, Smith, Shittu, Beevers, C.Taylor, Trotter, Hulse (Marquis, 85mins), Keogh, N'Guesan (Abdou, 66mins). Subs not used: M.Taylor, Tyson, Osborne, A.Smith, Saville.
Bookings: Shittu (42mins), Keogh (61mins), Beevers (76mins)
Scorer: Shittu (42mins)
Ref: M. Clattenburg