[1] James Dunbar-Nasmith was born in Devon,[2] the son of Admiral Sir Martin Dunbar-Nasmith, VC KCB KCMG (1883–1965) and Beatrix Justina Dunbar-Dunbar-Rivers CBE.
His elder brother was Rear-Admiral David Dunbar-Nasmith, CB DCL (1921–1997).
He was in professional practice as a partner in Law & Dunbar-Nasmith, architects, Edinburgh (since 1957), and Hilger, Law & Dunbar-Nasmith, architects, Wiesbaden (since 1993).
[1] Dunbar-Nasmith was Professor and Head of the Department of Architecture at Heriot-Watt University, Edinburgh, and the Edinburgh College of Art, 1978–1988, and later Emeritus Professor at Heriot Watt University.
[3] Dunbar-Nasmith was appointed a Commander of the Order of the British Empire (CBE) in the 1976 Birthday Honours "for public services in Scotland",[4] and knighted in the 1996 Birthday Honours "for services to Architecture.