Chestnut Hill Ventures, led by John G Berylson, have agreed to the investment to help the club "develop and prosper whilst supporting and assisting with the urban regeneration project in the locality."
In return, Berylson is set to become non-executive chairman of Millwall Holdings and a director of the football club while his colleague, Demos Kouvaris, will also join both boards. Current chairperson Heather Rabbatts will revert to the position of executive deputy chairman.
In addition to these monies, a further sum of around £1.5 million wil be raised by other parties while former chairman Peter de Savary is said to be investing another £500,000.
"This is tremendous news for Millwall and our supporters," gushed Rabbatts. "It enables us to move forward with confidence and continue to plan for future success both on and off the field."
Rumours that the money is to be used to pay off Kevin Braniff's goal-scoring bonuses this season are unfounded.