Elephant and Castle's Amelia Street, part of the Pullens Estate, is undergoing a facelift and residents demanded improved public space.
Dallaspierce came up with the winning design, called Abundant Amelia. It features window boxes, climbing plants and lighting to illuminate prominent trees.
The Pullens Tenants & Residents Association, the Architecture Foundation, First Base and London Borough of Southwark organised the competition to redesign the space.
Other shortlisted firms were Green Door, North Seven, Sprunt and Carl Turner Architects.
The winning design aims to "return a sense of ownership to the public realm for all users", said Dallaspierce director Jonathan Dallas.