Keepmoat will redevelop a former industrial site to provide a mix of traditional two and three storey houses and apartment blocks.
Keepmoat Homes is buying the land from the Homes & Communities Agency (HCA) and is looking to build up to 100 homes per year.
Chief executive Peter Hindley said: "This is an absolutely fantastic win for Keepmoat. Delivering this project will help us achieve our target of building more than 4,000 affordable new homes in the UK, helping meet the demand for quality housing stock. We are delighted to support the HCA in this important project, and we look forward to delivering it.”
Regional managing director Roland Grant added: “The Northfleet site is a landmark development for Keepmoat Homes and represents the largest and most significant award in the area, since we expanded the business in to London and the southeast in 2014.”