Festing graduated in 1987 as a Bachelor of Medicine from the London Hospital Medical College. He worked as a medical doctor for three years before leaving medicine in 1990 to study Environmental Technology at Imperial College, graduating with an MSc in 1991.
Festing did voluntary work for Greenpeace from 1992 to 1994, before joining Friends of the Earth in 1994, where he was employed as their transport and wildlife campaigner until 1998. He worked as a campaign leader for Help the Aged from 1998–1999, then became Director of Public Dialogue for the Association of Medical Research Charities, an umbrella group representing 100 medical-research charities, a post he held from 2000 until 2004, when he joined the Research Defence Society (RDS). He was chief executive of Understanding Animal Research (formally RDS) from 2004 until June 2011, when he joined the Society for General Microbiology.
Simon Festing is the son of Michael Festing, a member of the UK Animal Procedures Committee, and former trustee of the Fund for the Replacement of Animals in Medical Experiments. He is divorced and has two children. His former wife is author Ismat (Issy) Festing, who is also a dentist.
In December 2005, Festing appeared on a British reality TV show, The Devil's Challenge, in which he was subjected to procedures used in animal labs, later engaging in an online debate with John Curtin, an animal-rights activist.
- http://www.channel4.com/more4/event/K/killorcure/animals_simonfesting.html Archived February 24, 2006, at the Wayback Machine.
- Goodale, Greg; Black, Jason Edward (2010-). Arguments About Animal Ethics. Lexington Books. p. 144. ISBN 9780739142981. Retrieved 26 August 2012. Check date values in:
- http://www.channel4.com/more4/documentaries/doc-feature.jsp?id=20 Archived February 26, 2006, at the Wayback Machine.
- http://www.channel4.com/community/showcards/A/Animals.html Archived June 18, 2006, at the Wayback Machine.