He had three siblings: two brothers, Jonathan Dimbleby, also a television current affairs presenter, and Nicholas (died 2024), and a sister, Sally.

The two younger Dimblebys both made their television débuts in the 1950s in the BBC's first holiday programme Passport, at a time when the whole family would visit resorts in Switzerland or Brittany.

After learning French in Paris and Italian in Perugia, Dimbleby read Philosophy, politics and economics at Christ Church, Oxford and graduated with a third-class degree.

On 24 July 1967, Dimbleby was one of seventy signatories to an advertisement in The Times advocating the decriminalisation of cannabis use, which had been written by campaigner Stephen Abrams.

Dimbleby served as chairman of the BBC's Thursday evening topical debate programme Question Time from 1994 until 2018.

He has instead remained, according to Mark Duguid for the BFI's screenonline website, best known for his "gravitas, journalistic integrity and consummate professionalism" and as "a paragon of impartiality"[13] as a narrator and moderator, of British politics.

In 2005, he hosted a BBC One series, A Picture of Britain, celebrating British and Irish paintings, poetry, music and landscapes.

On 12 November 2009, Dimbleby missed his first Question Time in over fifteen years, having been taken to hospital as a precaution after being briefly knocked out by a rearing bullock at his farm in Sussex.

[23] Presenting from BBC Television Centre Studio 1, he was an anchor, and involved in commentary contributions, guest interviews and introducing live outside broadcasts.

It looks as if the gap is going to be something like 52 to 48...so a four point lead for leaving the EU, and that is the result of this referendum which has been preceded by weeks and months of argument and dispute and all the rest of it.

In 2019, and in some of his first work outside the BBC for decades, he presented an acclaimed series of podcasts on the life of media mogul Rupert Murdoch entitled The Sun King.

This focused on various key moments in Murdoch's professional career such as his takeover of newspapers around the world, Fox News, his battles with print unions and the phone hacking scandal.

[26] In September 2022, Dimbleby came out of retirement to commentate on the state funeral of Queen Elizabeth II for the BBC, in particular for the committal service at St George's Chapel, Windsor.

[28] Although the brothers presented election coverage on competing channels, when asked in an interview about rival ITV's plans to include a riverboat party with the likes of Kevin Spacey and Richard Branson in their 2005 election broadcast, Dimbleby commented, "They've got Jonathan Dimbleby, what do they need Kevin Spacey for?

[30] In 2000, Dimbleby married Belinda Giles, a granddaughter of Herbrand Sackville, 9th Earl De La Warr,[31] with whom he had a son, Fred, in February 1998.