Three goals in seven crazy second-half minutes cost Millwall dear as The Lions slipped to their first defeat in three games.
Trailing to a sublime David Prutton first-half strike, any hopes the visitors had of getting back into the game were effectively destroyed when Jermaine Beckford (52mins) and a Jonathan Douglas brace (56 and 59mins) left Millwall looking dead and buried.
Despite a stirring fightback in which Will Hoskins (64mins) and debutant Ahmet Brkovic (75mins) reduced the arrears, the damage had already been done and it was too high a mountain to climb.
It had all started so brightly for The Lions, who had the ball in the back of the net after just two minutes when Gary Alexander slipped the ball through to Hoskins, only for the striker's flicked finish past Casper Ankergren to be ruled out for offside.
On seven minutes Hoskins saw his header from a Brkovic cross fly over the bar, whilst Danny Senda twice tried his luck with a chipped effort that drifted wide and then a 22-yard freekick that was blocked.
After a subdued start, Leeds gradually began to work their way into the game and Seb Carole's fierce drive was well held by keeper Lenny Pidgeley, making his first senior appearance of the season.
On 24 minutes Tresor Kandal really should have done better when he met a delicious deep delivery from Fraser Richardson, only to power his header wide with the goal at his mercy.
Beckford sent a rasping shot on the turn narrowly off-target after 32 minutes, and three minutes later the home side had taken the lead. Former Brighton winger Carole was the creator with a superb run and cross from the left, and Prutton lashed the ball into the top corner with a strike to savour.
Leeds came close to adding a second on 39 minutes, but this time Pidgeley produced a flying save low to his right to parry Douglas' piledriver.
Millwall could have sneaked an equaliser just before the break, only for Jamie O'Hara to snatch at his shot and screw the ball wide after Brkovic's cross had eluded the home defence.
O'Hara was denied an equaliser seconds after the restart when his whipped in delivery was pushed onto the foot of the post by Ankergren in the home goal.
But little could The Lions or the travelling fans have expected the craziness that was to follow.
The turning point came on 52 minutes when Pidgeley's attempted clearance bounced off Kandol's head and fall straight into the path of Beckford, who strode forward and gleefully despatched a low angled drive into the empty net.
Four minutes later Douglas capitalised on some slack marking following a corner and stabbed home Leeds' third. Before the celebrations had died down shell-shocked Pidgeley was picking the ball out of the back of his net for a fourth time after Douglas' 20-yard freekick went straight through a 10-man wall.
The introduction of Jay Simpson for Ali Fuseini saw Brkovic switch to a central midfield role and the teenage striker sparked The Lions into life.
Within seconds of entering the fray he teed up Hoskins, whose fierce drive was superbly tipped round the post by Ankergren for a corner.
Hoskins was not to be denied, and on 64 minutes Simpson's cross was only half-cleared and there was the striker to slam home his second goal in as many matches.
Incredibly even though The Lions were 4-1 down you got the feeling that if they could add a second goal quickly, it really would be game on.
Unfortunately when a gilt-edged opportunity presented itself to O'Hara two minutes later the youngster's effort flew wildly over the bar from 12 yards.
But credit to The Lions, they kept plugging away and further reduced the arrears 15 minutes from time with a superbly crafted goal. Andy Frampton and O'Hara combined down the left, with the latter's incisive cross powerfully headed past Ankergren by Brkovic.
Despite a barn-storming finish to the match, it was simply too much to ask for The Lions to claw back a further two goals with those seven mad minutes sadly proving so very costly.

Leeds United: Ankergren, Richardson, Douglas, Marques, Heath, Prutton, Beckford (Da Costa, 90mins), Westlake, Carole (Weston, 77mins), Kandol, Clapham. Subs not used: Lucas, Huntington, Andrews.
Booking: Prutton (76mins)
Scorers: Prutton (35mins), Douglas (56, 59mins), Beckford (52mins),

Millwall: Pidgeley, Senda, Frampton, Fuseini (Simpson, 61mins), Robinson, Shaw, Dunne, Alexander, Hoskins, O'Hara, Brkovic. Subs not used: Day, Harris, Whitbread, Barron.
Bookings: O'Hara (67mins), Brkovic (78mins)
Scorers: Hoskins (64mins), Brkovic (75mins)

Ref: Mark Halsey
Att: 3,319 (Away 856)