Ed Upson struck a late, late winner to secure Yeovil Town's first-ever Championship win as Millwall slipped to defeat on the opening day of the season.
Gary Johnson's Championship new-comers had spent long spells of the game, especially the second half, withstanding a tide of Millwall pressure.
But up popped midfielder Upson with just two minutes remaining to fire home through a crowd of players beyond the reach of David Forde in the Millwall goal.
It was not the sort of start that Den boss Steve Lomas had wanted as his new-look side huffed and puffed without failing to break through a resilient Yeovil rearguard.
The opening half proved a fast and furious affair and Millwall twice went close to breaking the deadlock in the first 15 minutes.
Steve Morison, making his second debut for The Lions following his summer move from Leeds United, failed to make the most of the space allowed him and headed Shane Lowry’s delivery wide of the mark before Andy Keogh then headed off target from a near-identical position just moments later.
Yeovil fired an early warning of their own when Upson spotted keeper Forde off his line and despatched an audacious lob that dropped onto the roof of the net from fully 40 yards.
Forde was called into action just past the quarter-hour mark, smothering the ball on the line after Dan Seaborne's header from an Upson free-kick nearly squirmed over.
However it was Millwall who went closest to breaking the deadlock on 24 minutes when a quick, slick move involving Morison and Alan Dunne set up James Henry, whose goalbound effort was superbly charged down by Yeovil keeper Marek Stech.
At the other end Luke Ayling's left foot drive flew narrowly wide; Millwall responded with Henry's persistence on the right picking out Keogh, but the latter scooped over the bar.
Defenders Danny Shittu and Mark Beevers both tried to use their physical strength to Millwall's advantage from corners at the end of the first half and beginning of the second, but Yeovil held firm.
The introduction of Nicky Bailey for Josh Wright added fresh impetus for The Lions and Stech again came to the rescue with another smart stop to deny Henry.
On the hour mark the keeper's sidefooted clearance fell invitingly for Henry, he in turn controlled the ball but then contrived to send his lob over an open goal from around 25 yards.
Despite enjoying most of the possession, Millwall's lack of a killer touch in front of goal was to prove so costly when with two minutes left, The Lions were unable to properly clear their lines. The ball fell for Upson and he made no mistake firing through a crowded area beyond the stranded Forde.
Morison went close to conjuring up an injury time leveller, only to power a header from sub Liam Feeney's delivery wide of the mark with the last real goalmouth action of the game.
Millwall: Forde, Dunne, Lowry, Abdou, Shittu, Beevers, Chaplow (Feeney, 82mins), Wright (Bailey, 50mins), Morison, Keogh (McDonald, 68mins), Henry. Subs not used: Bywater, Easter, Robinson, Malone.
Booking: Morison (14mins)
Yeovil Town: Stech, Ayling, Webster, Seaborne, Tate, Dawson, Upson, Edwards, Foley (Hoskins, 80mins), Hayter (Davis, 90+1mins), Madden (Ngoo, 46mins). Subs not used: Stewart, Moore, Clifford.
Bookings: Seaborne (14mins), Madden (19mins)
Att: 12, 404 (away 891)