Leeds United fans shamed their club as they refused to observe a minute silence to honour the memory of former Manchester United great George Best who died earlier this week.
The referee Mick Fisher was forced to end the tribute midway through as the travelling fans sang anti-Manchester United songs to the disgust of everyone at the ground.
The match was a predictably ugly affair with both sides contesting every ball in a congested midfield and produced more yellow cards than clear-cut chances for a goal.
Ben May deflected David Healy's shot into his own net in injury time to earn the visitors all three points.
Colin Doyle was leading a charmed life in the Millwall goal on his debut for the club following his deadline day loan move from Birmingham City.
Doyle, 20, twice had his right hand post rattled in the first 20 minutes by the Leeds forwards.
On 13 minutes Eddie Lewis found a yard of space inside the box and fired a snap shot low through a crowded box only to see the ball cannon off the upright and wide for a goal-kick with Doyle beaten.
Just five minutes later David Healy hit a well struck shot from just inside the box against the post and the Millwall defenders smuggled the ball away.
Midway through the half the rookie keeper was called into action again when a poor pass from Adie Williams was intercepted by Healy, but he dashed out of his goal to save well at the feet of the Northern Ireland international.
Millwall continued to press and contest the midfield but lacked quality in the final third as Leeds looked the more likely to score, but the Millwall defence refused to buckle.
In first-half injury time substitute Jonathan Douglas, on for the injured Shaun Derry, sprang the Millwall offside trap and ran in goal, but the on-loan keeper again made a crucial save.
Referee Fletcher did well to keep a lid on this fiery contest that threatened to boil over at any point.
Just minutes later Millwall new boy Zak Whitbread, booked just after the restart, was lucky to escape with the stern word from the referee when he hauled down Rob Hulse on the edge of the box.
The home side almost sneaked a win when Neil Sullivan tipped Barry Hayles' shot over the bar late on.
Doyle capped his man of the match display with a point-blank save from Douglas in the dying minutes, only for Healy to conjure the winner with the last kick of the match just a minute later.