McKenna has written and produced books and multimedia products, hosted self-improvement television shows and presents seminars in hypnosis, neuro-linguistic programming, weight loss, motivation and the Zen meditation Big Mind and Amygdala Depotentiation Therapy (ADT).
McKenna became interested in hypnotism as a result of a guest who appeared on his show. His interest stemmed initially for reasons of self-development, although entertainment was later to play a big part. Whilst still working at Capital Radio, McKenna began experimenting with small hypnotic shows, first for the amusement of friends, then for audiences in pubs and clubs. From there he starred in a regular Sunday night show at the Duke of York's Theatre, which was owned at the time by Capital Radio. The success of those shows led to his playing other theatres across the UK, Ireland, The Netherlands, the US, Australia and Hong Kong.
After a brief spell at Radio 1 in the early 1990s, McKenna decided to quit radio. In 1993, ITV broadcast The Hypnotic World of Paul McKenna, which featured audience members volunteering to be hypnotised to act in comedic ways, the show subsequently being aired in 42 countries. During this time, McKenna continued to study hypnosis, and neuro-linguistic programming with Richard Bandler, the co-creator of NLP.
McKenna hypnotised Top Gear presenter Richard Hammond on series 4, episode 2 of the motor show in 2004. In October 2009 McKenna was a guest on Private Passions, the biographical music discussion programme on BBC Radio 3.
McKenna has become one of the most successful non-fiction authors in the world with self-help titles including 'I Can Make You Thin', 'Stop Smoking Without Gaining Weight', 'I Can Make You Happy' and 'Hypnotic Gastric Band' included in a wide range of highly popular titles published in countries across the world.
McKenna hypnotised The One Show presenter Matt Baker to believe that he was Pablo Picasso during which time he created several impressionist pieces of art, which were shown on air while the footage was played back during McKenna's appearance on 9 January 2013.
McKenna has also presented several live events including Get The Life You Want with Paul McKenna and Richard Bandler and Get Thin.
Recently Dr McKenna has been involved in the research and development the Psychosensory therapy of Amygdala Depotentiation Therapy (ADT) otherwise known as Havening  with Dr. Ronald Ruden and Dr. Stephen Ruden, presenting seminars to health care professionals in the UK and USA. He specializes in working with PTSD, severe trauma, pain control and emotional overwhelm.
McKenna attended St Ignatius College in London and East Hertfordshire College and holds two doctorates; the first from LaSalle University (Louisiana) and the second from the International Management Centres Association (IMCA). In 1996, McKenna was granted a PhD from LaSalle University. This university was legally licensed by the state, but it falsely claimed to be an accredited university. After the principal of LaSalle pleaded guilty to fraud, thousands of students, including McKenna, were awarded compensation from the U.S. government.
In 2003, McKenna gained a degree of Doctor of Philosophy by Explication (DPhil) from the International Management Centres Association (IMCA) whilst it was still accredited by the US Distance Education and Training Council (DETC). The title of his thesis was "The Effects of Fixed Action Patterns and Neuro-Linguistic Programming in Determining Outcomes in Human Behaviour".
In 2006, McKenna successfully sued and won relatively small damages against the Daily Mirror for libel over claims made by Mirror columnist Victor Lewis-Smith that McKenna's degree from LaSalle was merely a purchased "bogus degree", bought with the intention of deliberately defrauding the public.
McKenna has produced self-help books, CDs and DVDs as well as several audio books that provide the information from the books in audible form. His guides and manuals have been worth just shy of £17m to UK book retailers in the 21st century, according to Nielsen BookScan data. McKenna's book I Can Make You Thin as "the best-selling weight loss book ever". His latest book is Hypnotic Gastric Band.
McKenna's full list of published titles include:
- Hypnotic Gastric Band Bantam Press 2013 ISBN 978-0-593-07074-1
- I Can Make You Smarter Bantam Press 2012 ISBN 978-0-593-06405-4
- I Can Make You Happy Bantam Press: 2011 ISBN 978-0-593-06404-7
- Change Your Life in Seven Days - Updated version Bantam Press: 2010 ISBN 978-0-593-06661-4
- I Can Make You Confident, Sterling Publishing: 2010. ISBN 1-4027-6922-9
- I Can Make You Sleep, Bantam Press: 2009. ISBN 1-4027-6574-6
- I Can Make You Rich, Bantam Press: 2007. ISBN 0-593-05537-3
- Quit Smoking Today Without Gaining Weight, Bantam Press: 2007. ISBN 0-593-05536-5
- Instant Confidence, Bantam Press: 2006. ISBN 0-593-05535-7
- I Can Make You Thin, Bantam Press: 2005. ISBN 0-593-05054-1
- Change Your Life in Seven Days, 2005.ISBN 0-593-05053-3
- How to Mend Your Broken Heart, (with Hugh Willbourn) Bantam Press: 2003. ISBN 0-593-05055-X
- The Power to Influence, Nightingale-Conant: 1998. ISBN 1-905453-56-6 (audiobook with Michael Breen)
- The Paranormal World of Paul McKenna, Faber and Faber: 1997. ISBN 0-571-19245-9
- Paul McKenna's Hypnotic Secrets, Boxtree: 1995. ISBN 0-7522-0192-1 (with Peter Willis and Clare Staples)
- The Hypnotic World of Paul McKenna, Faber and Faber: 1994. ISBN 0-571-16802-7
McKenna has also released a number of audio recordings including Sleep Like a Log, Eliminate Stress, Positive Self-Image, Attracting Wealth, Inner Happiness, Supreme Self-Confidence, Stop Smoking for Good. He also wrote the foreword to Nikolic, Seka and Sarah Tay, You Can Heal Yourself: Bio-energy and the Power of Self-healing.
McKenna learned hypnosis and NLP from Richard Bandler, co-creator of Neuro-Linguistic Programming. He uses Thought Field Therapy in many of his television demonstrations and studied under Roger Callahan, the creator of TFT. He also teaches the Zen meditation 'Big Mind'. He presents the process with its creator, American Zen Master Dennis Genpo Merzel Roshi, abbot and founder of Kanzeon Zen Center in Salt Lake City, Utah..
On Sunday, October 26, 2014, Paul McKenna and Kate Davey became engaged.
On Sunday July 26, 2015, The Mail on Sunday newspaper printed details of a legal action between McKenna and his "platonic wife" Clare Staples who has made allegations of "booze and drug-filled parties" hosted by McKenna, and that he has "struggled to varying degrees for many years with addictions to cocaine, alcohol, various prescription pills and other addictions".
- Vernon, Polly (12 December 2012). "'Look in to my eyes'" (Interview with Paul McKenna). The Observer (London). Retrieved 4 February 2014.
- The Sun
- Norman, Neil (16 July 2006). "Paul McKenna: The eyes have it" (profile). The Independent (London). Retrieved 4 February 2014.
- "Private Passions: Paul McKenna" (programme listing). BBC Radio 3. 11 October 2009. Retrieved 4 February 2014.
- "Hypnotist McKenna sues over degree claim". The Scotsman (Edinburgh). 11 July 2006. Retrieved 4 February 2014.
- McKenna, Paul (2003). "The Effects of Fixed Action Patterns and Neuro-Linguistic Programming in Determining Outcomes in Human Behaviour" (Abstract of DPhil explication). International Management Centres Association. Archived from the original on 13 October 2007. Retrieved 4 February 2014.
- "Paul McKenna wins court battle over fraud claims - at a price". The Daily Mail (London). 28 July 2006. Retrieved 4 February 2014.
- "McKenna wins 'fake degree' case". BBC News. 28 July 2006. Retrieved 4 February 2014.
- Bhattacharyya, Gargi (3 August 2006). "McKenna the brave" (editorial). The Guardian (London). Retrieved 4 February 2014.
- "Paul Mckenna talks Hypnotic Gastric Band with HELLO! Online". HELLO! Online. 14 February 2013. Retrieved 4 February 2014.
- The Sun
- Sidgwick & Jackson Ltd.: 2006. ISBN 0-283-07038-2
- Official website
- Paul McKenna at the Internet Movie Database
- Hello Magazine interview with Paul McKenna
- The Sun - We Lost Over 13 and a Half Stone with 'Gastric Band' Hypnosis feature with Paul McKenna