Robert Snodgrass scored twice in three second-half minutes as Leeds United paid a moving tribute to former player Gary Speed, who died last Sunday.
Snodgrass opened Leeds' account with a stunning 62nd-minute free-kick that gave Steve Mildenhall no chance in the Millwall goal.
Barely three minutes later Mildenhall was picking the ball out of his net for a second time when he was unable to prevent Snodgrass' header from a Lloyd Sam delivery crossing the line, despite getting a hand to the ball.
Prior to kick-off Lions boss Kenny Jackett and his Leeds counterpart Simon Grayson along with former players Gordon Strachan, David Batty and Gary McAllister laid wreaths on the pitch following a video montage and minute's applause for Speed, who played in United's 1992 title-winning side.
It was difficult to tell whether the sheer weight of emotion surrounding the occasion had an effect on both teams, but the game was, for long spells, forgettable as a spectacle.
What could not be doubted was the high esteem with which one of United's favourite sons was held by the Elland Road faithful.
Speed's name was chanted for 11 minutes from the 11th minute in recognition of his shirt number, the sound reverberating around all four sides of Leeds' famous old ground.
It was Millwall though, who conjured up the best scoring chance of the opening half when Darius Henderson, back in the side along with skipper Paul Robinson, saw his goalbound header from a Liam Feeney corner pushed away at full stretch by home keeper Alex McCarthy.
"We had the best chance of the first half," said Lions boss Kenny Jackett, "But their keeper made a good save from Darius Henderson.
Once the first goal went in for Leeds though, the atmosphere stepped up and it was very difficult for us.
It was tough for us to come here today and get a result. We did well for an hour, but after they scored their first, and then second quickly, we didn't quite have enough to test Leeds."
United, lost midfielders Johnny Howson and Michael Brown to injuries before the break, with Brown inexplicably avoiding punishment for an awful challenge on Liam Trotter, as did Snodgrass for a crude tackle on the tireless Jimmy Abdou after just five minutes.
Despite having to shuffle their playing pack, Leeds looked a little more dangerous in the final third, with sub Andy Keogh's header well held by Mildenhall and then Lloyd Sam volleying high and wide from a couple of yards following a deep delivery from the left.
Winger Snodgrass finally broke the deadlock when he curled a sublime free-kick from 25 yards past Mildenhall and into the top right corner.
Three minutes later he doubled the lead, timing his run to meet Sam's right-wing cross to perfection and heading home Leeds' second of the game.
Hamer Bouazza and then James Henry entered the fray for The Lions, but it was Mildenhall who was the busier of the two keepers, producing fine reflex saves to deny both Luciano Becchio and then Sam late on.
At the other end Henry drove straight into keeper McCarthy's hands and before sub Darren Ward's header was comfortably collected by the keeper in injury-time.
"It's been a difficult week for everyone here," said Leeds boss Grayson. "It was so fitting that we won this game and that everyone realised just what Gary Speed contributed to football."
Leeds United: McCarthy, Connolly, Kisnorbo, Brown (Keogh, 40mins), Becchio, Howson (Sam, 36mins), Clayton, Pugh, Lees, Snodgrass, White. Subs not used: Taylor, Nunez, Bromby.
Booking: Kisnorbo (47mins)
Millwall: Mildenhall, Smith, Baker, Abdou, Robinson, Lowry (Ward, 85mins), Barron (Bouazza, 68mins), Trotter, Henderson, Simpson, Feeney (Henry, 73mins). Subs not used: Allsop, Marquis.
Bookings: Baker (70mins), Trotter (73mins)
Ref: M. Oliver