Designed by Richard Murphy Architects, the Fife building was one of a record 57 entered for the 2017 Edinburgh Architectural Association (EAA) Awards.
This is the second year that Mr Murphy’s firm has claimed the title.
The 2,300 m2 contemporary extension links the town’s Carnegie Library with a new gallery and exhibition space and was commissioned by Fife Council following a design competition.
It is located within Dunfermline’s Heritage Quarter, which contains several historic buildings of national significance, such as the medieval Dunfermline Abbey and Abbot House, one of the few intact 15th century buildings left in the country.
EAA vice president and head judge Julie Wilson said: “The judges were unanimous when it came to agreeing the building of the year. The winner is a beautifully crafted building, which is a rich, mature piece of architecture.”
Architect Richard Murphy said: “Of course the building is not in Edinburgh, although in the Association’s patch, and we are very pleased that it beat several strong contenders from within the city.
“It is a great credit to Fife Council to have held firstly an architectural competition and then to have followed through with the vision over the intervening ten years to finally realise what we hope will be an innovative building that will be taken to the hearts of the people of the town and beyond.
“A contemporary building at the heart of a conservation area is not an easy project to bring about but we hope that this building, in the fullness of time, will take its place alongside its historic neighbours as part of a continuing development of the town’s illustrious history.”