Built on a previous site of housing, a church and the Senegal Fields playgrounds, the Den has an all-seated capacity of 20,146, although that is restricted to approximately 18,100 to allow for visiting fans' segregation and crowd safety measures.

The New Den, as it was initially known to distinguish it from its predecessor, was the first new all-seater stadium in England to be completed after the Taylor Report on the Hillsborough disaster of 1989.

[3] Millwall played their final game at The Old Den on 8 May 1993 after 83 years and then moved to the new stadium a quarter-of-a-mile away from Cold Blow Lane.

However, their dreams of Premier League football were ended by a defeat in the playoffs and they were relegated to Division Two in 1996, not winning promotion from that level until 2001.

In September 2016 Lewisham Council approved a compulsory purchase order of land surrounding the Den rented by Millwall, as part of a major redevelopment of the "New Bermondsey" area.

The plans are controversial because the developer, Renewal, is controlled by offshore companies with unclear ownership, and is seen by the club and local community to be profiteering by demolishing existing homes and businesses as well as Millwall's car-park and the highly acclaimed and well recognised Millwall Community Trust—to build up to 2,400 new private homes, with no council housing and less than 15% of 'affordable housing'.

[6] In October 2019 Lewisham Council terminated the conditional land sale agreement with Renewal, ensuring the stadium's future.

[8] In June 2021, Renewal submitted new plans for its housing development by the Den, with 3,500 new homes in towers of up to 44 storeys over a 15-year period.

Around 150 celebrities took part including McFly, Tony Hadley, Amy Winehouse and ex-Millwall fan favourite Terry Hurlock to raise money for the charity.

[13] The Den doubles as The Dragon's Lair, home ground of Harchester United in the TV series Dream Team.

It was used to film The Bill episode of Gun Runner: Kick Off featuring their home game against Leyton Orient in March 2008 (aired on ITV in July 2008).

In 2010, Kit Kat made their own 'Cross your Fingers' advert using clips from Arsenal, West Ham, Oxford United and also Millwall's Den.

[16] Construction of New Bermondsey railway station, a London Overground line adjacent to the Den, began in 2012 but then stalled as plans for a major development were delayed.