Paul McKenna started in radio aged 16 at in-store Radio Topshop, and went on to present for stations including Radio Jackie, Radio Caroline, Chiltern Radio, Capital Radio and BBC Radio One.

A hypnotist who guested on his show led to a developing interest in the subject, initially for reasons of self-development, although entertainment was later to play a big part. Whilst still working at Capital, he began experimenting with small hypnotic shows, first for the amusement of friends, then for audiences in pubs and clubs. McKenna then started doing regular Sunday night shows at the Duke of York's Theatre, which was owned at the time by Capital. 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.

Many of McKenna's one-to-one hypnotherapy clients are celebrities including Ellen DeGeneres and David Walliams, who used McKenna to help with his swim across the English Channel.

In the 1990s, McKenna presented a number of TV programmes including The Hypnotic World of Paul McKenna (1993—1995), Paul McKenna's Paranormal World (1997) and Hyp the Streets (1999). In January 2008, the Discovery Channel signed a £23 million deal with McKenna to make a series of self-help programmes. To date, the deal is the largest ever for a British TV personality. The first of his I Can Make You Thin programmes aired on TLC, The Learning Channel on 16 March 2008.

In October 2009 he was a guest on Private Passions, the biographical music discussion programme on BBC Radio 3.

McKenna attented St Ignatius Secondary School in London.McKenna holds two doctorates; the first from LaSalle University and the second from the business school International Management Centres Association (IMCA). In 1996, after two years of study on a 70,000-word thesis, McKenna was granted a PhD from LaSalle University. This university was properly licenced by the state of Louisiana, but falsely claimed to be an accredited university. After the principal of LaSalle pleaded guilty to fraud, along with thousands of other students, McKenna was awarded compensation from the U.S. government.

In 2004, McKenna completed an APEL and subsequently gained a UK accredited doctoral degree DPhil from the business school International Management Centres Association (IMCA), which is accredited by the British Accreditation Council (BAC). 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 the Daily Mirror for libel, over claims made by journalist Victor Lewis-Smith that McKenna obtained a "bogus degree" merely for money to deliberately defraud the public (the degree was from LaSalle University ). McKenna won the case and substantial damages. The court stated, "Mr McKenna was not, in my judgment, dishonest and, for that matter, whatever one may think of the academic quality of his work, or of the La Salle degree, it would not be accurate to describe it as 'bogus'." "Desmond Browne, QC, for McKenna, said that 'any perceived lack of academic rigour at La Salle' did not prove that his client was dishonest."

McKenna has produced a range of self-help books, CDs and DVDs. In 2006 his book sales alone reached £3.5m. His guides and manuals have been worth just shy of £17m to UK book retailers in the 21st Century, according to Nielsen BookScan data.

He has also published:

* 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 (with Hugh Willbourn) ISBN 0-593-05053-3

* How to Mend Your Broken Heart, 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, and 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.

McKenna uses Thought Field Therapy in many of his television demonstrations and studied under Roger Callahan, the creator of TFT. Roger Callahan, Ph.D. is a clinical psychologist. A graduate of the University of Michigan, Roger received his Ph.D. in clinical psychology from Syracuse University.

McKenna 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. He received transmission in both Soto Zen and Rinzai Zen. Merzel was the second Dharma Successor of Taizan Maezumi roshi, with whom he began his Zen practice in the 1970s.