Feilden was born in Hampstead, London. He was educated at Bedford School and The Bartlett School of Architecture, University College, London, completing his training at the Architetural Association after the second world war.
He joined the practice of Edward Boardman and Son in Norwich, where he designed the Trinity United Reformed Church. He set up an architectural practice, Feilden+Mawson, with David Mawson in 1956, to which offices in Norwich, London and Cambridge were later added. In 1968 Feilden took over as consultant architect to the University of East Anglia, completing the work of his predecessor Denys Lasdun, and creating an arena shaped square as a social space.
His work in Britain encompassed Norwich Cathedral, York Minster, St Paul's Cathedral, Hampton Court Palace and St. Giles' Cathedral, Edinburgh. Overseas he advised on Jerusalem's Al-Aqsa mosque, the Taj Mahal, the Konark Sun Temple and the Great Wall of China.
He was elected Director of the International Centre for the Study of the Preservation and Restoration of Cultural Property (ICCROM) in 1977. During his mandate he spearheaded safeguarding measures and disaster recovery of cultural heritage in the wake of the 1976 earthquakes in Guatemala and Friuli (Italy), and the 1979 earthquake in Montenegro.
His 1982 publication, Conservation of Historic Buildings is still an important reference book for architectural conservators.
He died on 14 November 2008 at the age of 89.
- Rizzi, Gionata (2009). "Sir Bernard Feilden 1919–2008: A Monument to Building Conservation". Journal of Architectural Conservation. 15 (1): 5–24. doi:10.1080/13556207.2009.10785036. ISSN 1355-6207.
- Fidler, John (20 November 2008). "Sir Bernard Feilden: Distinguished and prolific conservation architect whose work had global significance". The Guardian. Retrieved 11 September 2012.
- Muthesius, Stefan (2000). The Postwar University: Utopianist Campus and College. New Haven and London: Yale University Press. p. 149. ISBN 0-300-08717-9.
- Mounir Bouchenaki; Jukka Jokilehto (October 2009). "From Rome Centre to ICCROM: Milestones on the Path of the International Centre" (PDF). ICCROM Newsletter. Rome: ICCROM. 35: 4. ISSN 1010-2639. Retrieved 10 February 2010.
- "Sir Bernard Feilden: Conservation architect who brought his skills to Britain's cathedrals, the Great Wall of China and the Taj Mahal". The Telegraph. 16 Nov 2008. Retrieved 11 September 2012.