Alex Mowatt struck the only goal of the game to end Millwall's hopes of recording three away wins on the spin in a tight encounter at Elland Road.
Mowatt's strike, a deflected free-kick six minutes before the break, proved decisive as Millwall were left to rue squandering a hatful of missed opportunities in the second-half.
Lions boss Ian Holloway was forced to make one change to the team that started against Birmingham City with loan midfielder Michael Tonge ineligible to play against his parent club, handing a rare first-team start for Angel Martinez.
Both Millwall and Leeds had enjoyed midweek wins on their travels at Birmingham City and Reading respectively, but it was the hosts who started at a pace, and dominated much of the opening first 45 minutes.
With former Lions striker Steve Morison at his robust best, Holloway's side had to dig in and defend against what was at times a relentless onslaught from the home side.
Leeds forced three corners in the opening four minutes, but keeper David Forde commanded his area well and collected under pressure on all three occasions.
Sam Byram was a whisker away from breaking the deadlock on seven minutes, only to see his low shot through a packed penalty area flash inches wide of the right hand post.
Jos Hooiveld made a superb last-ditch tackle to slide the ball clear in a two-on-one situation and then showed his worth at the other end, powering a header narrowly over from Lee Martin's corner with Millwall's first attempt on goal on 17 minutes.
But it was the home side who made the all-important breakthrough shortly before half-time. Shaun Williams was penalised for a foul and Mowatt's resulting free-kick took a wicked deflection, giving Forde no chance in the Millwall goal.
It could have been worse for Millwall as Morison threaded a super pass through to Rudy Austin and the midfielder's acrobatic scissor-kick effort was saved at the second attempt by Forde.
The Lions introduced Lee Gregory for Stefan Maierhofer at the start of the second-half and nearly found themselves back on level terms soon after the restart when the sub won possession, slipped the ball through to Martyn Woolford, but he blazed the ball over the bar.
Boosted by the physical presence of Ricardo Fuller and energy of fellow sub Ed Upson, introduced on the hour mark, The Lions certainly enjoyed a more positive time of it, causing problems to the home team.
Millwall forced a handful of chances, but were left to rue not making any of them count.
Woolford hit a sweet left-foot effort that bounced inches wide, skipper Alan Dunne rifled a long-range effort off target before Woolford again went close with a crisply struck drive that flew narrowly over.
The home side responded and were close to doubling their tally 15 minutes from time when Mirco Antenucci set up Byram at the back post, but he skied the ball over the bar.
It took a magnificent last-ditch tackle by Dunne to avert the danger as Morison broke clear through on goal, however it was Millwall who so nearly grabbed a deserved leveller right at the death.
There seemed nowhere for Fuller to go when he picked up the ball with his back to goal, but showing great control and tenacity, he wriggled his way into the penalty area and squeezed in a left foot shot that clipped the side netting with the last real chance of the game.
Silvestri, Wootton, Bamba, Bellusci, C Taylor, Byram, Austin (Antenucci 70), Murphy, Cook, Mowatt, Morison. Subs not used: S Taylor, Berardi, Sloth, Adryan, Sharp, Cani.
Bookings: Austin (44mins), Mowatt (75mins), Cook (82mins)
Scorer: Mowatt (39mins)
Forde, Cummings, Dunne, Hooiveld, Harding, Angel, Williams, Woolford, Fabbrini (Fuller 60), Martnez (Upson 60), Maierhofer (Gregory 45). Subs not used: Archer, Beevers, Abdou, O’Brien.
Millwall:Bookings: Maierhofer (34mins), Angel (47mins)
Ref: P. Tierney