Former Leeds striker Tom Elliott and Jed Wallace silenced the home crowdat the deathafter United had overturned a 2-0 deficit early in the second half.
Leeds appeareddead and buried at half-time courtesy of goals from Aiden O’Brien and Lee Gregory, both laid on a plate by another ex-Leeds forward, Steve Morison.
Depleted by injuries and suspensions, Thomas Christiansen’s side’s problems mounted when Liam Cooper became the third Leeds player to be sent off in as many matches.
But, against all odds, Christiansen’s team talk at the interval had an instant impact with Pierre-Michel Lasogga, making his first Sky Bet Championship start since November, and Kemar Roofe turning the game on its head.
However, Elliott and Wallace ensured Neil Harris’ side ended their troubles on the road at the 14th attempt.
The result was harsh on play-off chasing Leeds following an inspired second-half performance, butthey are now without a win in five matches in all competitions.
The warning signs were there for the hosts from the off as Felix Wiedwald was forced to parry away a curling shot from O’Brien inside the opening few seconds.
Leeds started to wake up and Lasogga failed to beat Jordan Archer with two glorious chances in a matter of minutes.
But it was Millwall who took control and could have scored twice before they eventually broke the deadlock in the 19th minute.
After Gregory fired wide with only Wiedwald to beat, Wallace’s volley from the edge of the box somehow went in, only for a Lions player to be flagged offside for interfering with play.
However, O’Brien headed Millwall ahead at the back post from Morison’s cross moments later.
Things got worse for Leeds when Cooper was given his marching orders shortly before half-time for a late challenge on George Saville, which led to a touchline melee that saw both teams’ assistant managers sent to the stands.
And Millwall seemed to have put the game to bed in the 44th minute, Gregory converting Morison’s delivery before colliding with the far post after the veteran striker had outmuscled Ronaldo Vieira.
But Leeds got the response their manager and fans asked for as early as the 46th minute, Lasogga firing home from Roofe’s cutback.
Goalkeeper Archer then fumbled a deflected cross from debutant Laurens de Bock and Roofe managed to bundle the ball home in a goalmouth scramble to make it 2-2.
Lasogga took the roof off Elland Road just after the hour mark with a stunning left-footed strike from the edge of the box which nestled into the bottom corner.
Suddenly Millwall looked like a side who had collected just six points from a possible 39 on their travels prior to their trip to West Yorkshire.
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