Brandreth was born in Wuppertal, Germany, where his father, Charles Brandreth, was serving as a legal officer with the Allied Control Commission. After having moved to London with his parents at the age of three, Brandreth was educated at the Lycée Français Charles de Gaulle (as it is called today), Bedales School, where he met his friend Simon Cadell, and New College, Oxford.
He was President of the Oxford Union in Michaelmas Term, 1969 and edited the university magazine Isis. He was described in a contemporaneous publication as "Oxford's Lord High Everything Else". Christopher Hitchens suggested that Brandreth "set out to make himself into a Ken Tynan. Wore a cloak." He became a theatre producer, politician, journalist, author and publisher as well as, later, turning TV presenter.
In the 1970s he hosted the ITV children's show Puzzle Party.
Brandreth has appeared on Countdown more than 300 times in Dictionary Corner, making more appearances than any other guest, including Carol Vorderman's final episode in 2008. He also appeared on TV-am. He was known for his collection of jumpers, of which some were sold in a charity auction in 1993.
In 2006, he appeared on the television series That Mitchell and Webb Look, satirising his appearances in Countdown's Dictionary Corner on the fictional game show "Numberwang". In 2007, he guest-starred in the Doctor Who audio play I.D. In July to August 2009, he hosted the game show Knowitalls on BBC Two. In April 2010, he appeared on BBC Radio 4's Vote Now Show. He also makes a cameo appearance as himself in Channel 4 sitcom The IT Crowd in the episode "The Final Countdown".
A frequent guest on BBC television panel shows, he has appeared on three episodes of QI and six episodes of Have I Got News for You. He has also appeared in episodes of Channel 5's The Gadget Show and is a contributor to the BBC's early evening programme The One Show. He has appeared in two episodes of the TV adaptation of Just A Minute as part of the show's 45th anniversary. In 2013, he was a guest on the Matt Lucas Awards. He appeared on Room 101 while Paul Merton was host, successfully banishing the Royal Variety Performance and the OBE honours systems into Room 101.
Brandreth has presented programmes on London's LBC radio at various times since 1973, such as Star Quality. He frequently appears on BBC Radio 4's comedy panel game Just a Minute. He has appeared on several episodes of Radio 4's political programme The Westminster Hour, explaining his thoughts on how to make the most of being a government minister. From 2003 to 2005 Brandreth hosted the Radio 4 comedy panel game Whispers.
In 2006, Brandreth appeared in the Radio 4 comedy programme Living with the Enemy which he co-wrote with comedian Nick Revell, in which they appear as a former Conservative government minister and a former comedian. In 2010 he broadcast a Radio 4 documentary about his great-great-grandfather, Benjamin Brandreth, the inventor of a medicine called "Brandreth's Pills". He is the host of the BBC Radio 4 comedy panel show Wordaholics, first aired on 20 February 2012. He appeared on the Radio 4 programme "The Museum of Curiosity" in August 2017, to which he donated a button that was once owned by a famous actor.
Since the 1970s Brandreth has written various books about Scrabble, words, puzzles and jokes, for adults and children. He wrote an authorised biography of John Gielgud, the actor, as well as lipogrammic reworks of Shakespeare. In the 1980s, Brandreth wrote scripts for Dear Ladies, the television programme featuring Hinge and Bracket. Brandreth is also the creator of a stage show called Zipp! which enjoyed success at the Edinburgh Festival and had a short run in the West End.
Brandreth has kept a diary. In 1999, he published his diaries between 1990 and 2007, written during his days as a politician, called Breaking the Code.
In September 2004, Brandreth's book on the marriage of the Queen and the Duke of Edinburgh, Philip and Elizabeth: Portrait of a Marriage was published. In July 2005, he published a second book on the Royal Family, entitled Charles and Camilla: Portrait of a Love Affair, which concerns the three-decade love affair between Charles, Prince of Wales and Camilla, Duchess of Cornwall.
Brandreth has written a series of six works of historical fiction called The Oscar Wilde Murder Mysteries, in which Oscar Wilde works with both Robert Sherard and Arthur Conan Doyle.
Over the years he has written and appeared in a number of comedic one-man shows and toured in a number of venues. Shows have included The One-to-One Show in 2010–2011, Looking for Happiness in 2013–2014 and Word Power in 2015–2016.
Brandreth was a Conservative Member of Parliament (MP), representing the City of Chester, from 1992 to 1997. He proposed a Private Member's Bill which became law as the Marriage Act 1994. In 1995, he was appointed to a junior ministerial position as a Lord of the Treasury, with his role being essentially that of a whip.
He later published a book of his diaries from his time as a whip, Breaking the Code. After his parliamentary career, he broadcast some of his reminiscences on BBC radio as Brandreth on Office and The Brandreth Rules in 2001, 2003 and 2005. He has stated an opposition to the British honours system, and said he would never accept one himself. In 2013, he clarified this position, stating that he had "no fundamental objection to the honours system" and that he selected the honours system for Room 101, as he could "tell funny stories about it".
In August 2014, Brandreth was one of 200 public figures who were signatories to a letter to The Guardian opposing Scottish independence in the run-up to September's referendum on that issue.
He is a former European Monopoly champion, and President of the Association of British Scrabble Players, having organised the first British National Scrabble Championship in 1971.
He is also the President of The Oscar Wilde Society. The society was founded in September 1990, by a group of fans of Wilde and his work, it is a non-profit organisation that aims to increase knowledge, enjoyment and study of Wilde’s life, personality and works. It organises lectures, readings and discussions, as well as visits to places connected with him.
Brandreth hosts an annual Oscar Wilde party to celebrate the writer's birth. These parties are often attended by such people as Stephen Fry, Joanna Lumley, Derek Jacobi, Camilla, Duchess of Cornwall and Julian Fellowes. The venues are often places of interest in Wilde's life, for example the Langham where A Picture of Dorian Gray was commissioned. In August 2005, he appeared in a production of Shakespeare's Twelfth Night at the Edinburgh Festival.
He is an after-dinner speaker, and he held the world record for the longest continuous after-dinner speech, at 12 and a half hours, done as a charity stunt. With his wife he founded the Teddy Bear museum; formerly located in Stratford-upon-Avon for 18 years, it was relocated to the Polka Theatre in Wimbledon, London and as of 2016 it is on display at Newby Hall in Yorkshire. He is a patron of the National Piers Society and vice-president of charity Fields in Trust (formerly the National Playing Fields Association).
He was appointed as Chancellor of the University of Chester in December 2016.
Brandreth married Michèle Brown, a writer and publisher, in Westminster in 1973. They have three grown-up children: Benet, a barrister, Saethryd, a journalist, and Aphra, a government economist and mother of their first grandchild, Kiyo. and reside in Barnes, Southwest London.