Super sub Neil Harris stepped off the bench to head the winner as Millwall brought Norwich City's 16-game unbeaten run to an end in front of a season's best Den crowd.
Chris Martin had stunned the majority of the 14,374 fans with a third-minute opener for the in-form Canaries.
But Tony Craig scored his first goal of the season with a deflected 24th-minute effort to haul The Lions level before Harris, a 46th-minute replacement for Lewis Grabban, met Chris Hackett's cross to head the winner just five minutes after his introduction.
Victory was no more than Millwall - and the outstanding Jimmy Abdou in particular - deserved.
In Wes Hoolahan, Norwich possess a player widely believed to be one of the most skillful in the division, but such was the sheer persistence and determination of Abdou that his threat was nullified to such an extent Hoolahan was eventually subbed. Job superbly done by Jimmy.
In fact it was a job superbly done by his team-mates too with a display that again underlined Millwall's promotion credentials.
The afternoon got off to a memorable start for Lions fan Mark Garlick who netted the right result before kick-off when his marriage proposal on the pitch to girlfriend Amanda Flower was accepted and sealed with a kiss.
Millwall looked as if they might be in danger of kissing goodbye to their unbeaten League record in 2010 when Paul Robinson was penalised for a foul on Martin 22 yards out with barely three minutes on the clock. The Norwich man picked himself up and promptly despatched a pinpoint free-kick low into the bottom corner beyond the reach of keeper David Forde.
Liam Trotter lashed narrowly over on seven minutes following good work by Grabban and Craig, with Grabban's low grubber comfortably dealt with by Fraser Forster in the visiting goal soon after.
Hackett's 21st-minute effort was held by Forster as The Lions continued to prise and probe, and an equaliser duly arrived.
Grabban's fierce angled drive had been fumbled over the line by Forster for a corner on 24 minutes, and when Hackett's delivery was half-cleared, there was left-back Craig to smash the ball home from the edge of the area, albeit taking a slight deflection on the way.
Referee Grant Hegley handed out a couple of stern ticking offs to Michael Rose and Cody McDonald following over-exhuberant challenges on the excellent Alan Dunne.
Norwich had the best chance to edge ahead before the break when Russell Martin went on a rampaging run from deep inside his own half before seeing his goal-bound shot somehow pushed round the post by Forde.
On came Chopper at the start of the second-half - and within five minutes the talismanic striker had made his mark, heading home the 130th goal of his Millwall career.
With the tables turned, The Lions didn't stop there and continued to work tirelessly in a search of a third goal to kill off a free-scoring Canaries outfit who had scored 71 league goals prior to this match.
Paul Robinson headed narrowly wide from a deep Hackett delivery before the hard-working winger hit a sizzling first-time effort that flashed inches over the bar on 70 minutes.
Norwich boss Lambert had already introduced pacey wide men Anthony McNamee and Oli Johnson in a bid to try and stretch the Millwall defence, and with his last throw of the dice, he replaced Hoolahan with Zak Whitbread, whose introduction enabled veteran campaigner Gary Doherty to move upfield and bolster the attack.
Doherty's physical presence certainly resulted in a more direct approach by Norwich in the final 12 minutes, but The Lions absorbed everything thrown at them.
Indeed a slick break could have produced a third goal for Jackett's men seven minutes from time, but on this occasion Hackett overhit the final pass to Harris, who had peeled away unmarked in a great position.
At the other end, Michael Nelson's acrobatic overhead kick flew inches past the post after deflecting off Craig with the visitors' last real chance of the game.
Millwall promptly dealt with the four minutes of injury-time in the same controlled manner that they had the previous 90, and were worthy winners of an absorbing encounter.
Millwall: Forde, Dunne, Craig, Abdou, Robinson, Ward, Barron, Trotter, Morison, Grabban (Harris, 46mins), Hackett. Subs not used: Sullivan, Frampton, Grimes, Smith, Fuseini, Batt.
Scorers: Craig (24mins), Harris (50mins)
Norwich City: Forster, Nelson, R.Martin, Doherty, Hoolahan (Whitbread, 77mins), C.Martin, Lappin, Russell, Rose, McDonald (Johnson, 66mins), Smith (McNamee, 66mins). Subs not used: Rudd, Gill, Hughes, Adeyemi.
Scorer: Martin (4mins)
Ref: Grant Hegley
Att: 14,374 (away 2,865)