RIBA award for Canada Water Library, which opened last year.
The library scooped the Royal Institute of British Architects' regional London award, in the leisure category.
Each year, innovative building projects are recognised for their positive contribution to British architecture. This year Southwark establishments fared well with Bermondsey Island also receiving a regional award and the White Cube in Bermondsey receiving a national award.
Canada Water Library, designed by Piers Gough from CZWG architects, opened in November 2011 as part of a community-focused regeneration programme for the area.
Veronica Ward, cabinet leader for culture and leisure, said: "Canada Water Library is one of the borough's real architectural masterpieces and we are thrilled to be recognised.
"Both the library and the Canada Water Library Culture Space have been thoroughly enjoyed by our local residents who have positively responded to the numerous literature evenings, reading clubs and children activities on offer within the library."
Canada Water Library has also been shortlisted in the 'culture and community' category at the New London Architecture awards 2012.
An art gallery dedicated to science has launched its first exhibition after opening in September.