Urban Splash received this year's RIBA Crown Estate Conservation Award for its redevelopment of the Midland Hotel in Morecambe.
The prestigious award was presented as part of the Stirling Prize awards ceremony as recognition for the successful restoration of an architecturally significant building. It was presented to Urban Splash and architects Union North, who had worked with conservation architects Avanti on the project.
Tom Bloxham, chairman of Urban Splash, said: "This is fantastic news and is one of our greatest achievements to date."
Splash spent £11m restoring the 1930s Art Deco hotel once enjoyed by Coco Chanel, Wallace Simpson and Laurence Olivier. The 44-room hotel overlooks Morecambe Bay and has views of the Lake District. The Midland reopened in June 2008.
Family-run firm English Lakes Hotels signed a deal in spring 2009 to manage the Midland Hotel, the first in Splash's proposed portfolio of hotels around the country.
The news takes the total awards won by Urban Splash to 283. Of those 22 have been awarded by the RIBA.