The first 500 people through the door at the discount shop after 9am tomorrow will be given a £10 gift voucher, and Brixton steel band the London All Stars will entertain shoppers all day.
TK Maxx, which has more than 230 stores across the UK, has taken over the space left by the former the Rest is Noise bar.
The Bon Marche Centre is thought to be the first purpose built department store in the country, and opened its doors for the first time in 1877. In a partial return to its former retail glory (it was once a regional Selfridges), the new retail space will take over four floors and 31,000 square feet of the building, including four escalators and two lifts.
The Brixton Blog will be heading inside for a sneak preview from 8am tomorrow.