The reputation of their fans, seldom the greatest in number but unrivalled in their raucous backing, requires no elaboration.
If an opponent was not intimidated by the reception from the stands, the home team itself has rarely been shy to follow up with a reminder that you were on their patch and therefore needed to abide by their rules.
So when Derby County won the first game behind closed doors here 3-2 less than a fortnight ago, it presented a big question.
Without that passionate backing were Millwall hindered by empty stadiums more acutely than the rest?
In reality a disappointing run of home form predating the coroanvirus pandemic had been the biggest contributing factor to this evening’s visit of Swansea City becoming something of a last chance saloon as far as their play-off hopes were concerned.
A 1-1 draw was little help to them nor their opponents.
Gary Rowett’s team last tasted a home win in mid-January, drawing three consecutive games on top of losing to West Bromwich Albion before the break, placing them much lower than 11th in the niche home form table.
Against a Swansea side one place further up the table and featuring Chelsea loanee Conor Gallagher behind Liverpool’s Rhian Brewster, Millwall opened the scoring midway through the first half thanks to a well-worked move that started and finished with Mason Bennett.
It was immediately noticeable that the Millwall players’ own vocal chords were not quietened in these still unusual circumstances. There was certainly more oomph to their communication compared to other Championship sides.
Shouts of encouragement were combined with remonstrations towards the referee, James Linington, when they felt a decision had not gone their way and a healthy dose of trash talk for their opponents.
There was one particularly noticeable protest in added time when substitute Matt Smith went to ground in the penalty area and felt he should have had a penalty.
If it were not for a train passing by at the same time, the roar may have been audible at Canada Water.
Denied their biggest asset, then, Millwall made sure the Den retained some formidable characteristics.
For social distancing reasons, away teams must now change in the community hall behind the stadium and walk around before entering at the north-eastern corner. That decision is out of the hosts’ hands but a small discomfort for away sides nonetheless.
Although a cardboard cut out of the queen positioned among pictures of fans in the Dockers Stand brought some giggles, there was still plenty of bite to proceedings.
The big pity for Rowett was that his team could not capitalise on their single-goal advantage.
Jed Wallace had goalkeeper Freddie Woodman, one of the few Swans capable of meeting Millwall in the shouting stakes, beaten nearing the half hour mark but visiting captain Matt Grimes cleared off line.
For long spells Millwall played the more incisive football. Gallagher did have a couple of half-chances from distance, the second a goalbound effort deflected for a corner by the head of Ryan Woods, while still scoreless.
But Swansea had not really threatened until Brewster found the net via the underside of the bar with a delightful free kick after Gallagher was clattered on the edge of the penalty arc.
At full-time players from both sides fell to their knees. While too often the apparently impossible has become achievable in this division, this stalemates suggests their respective Premier League dreams appear dead.
Still, the three remaining sides who must come to Bermondsey in the next month would be foolish to expect an easy ride.