Brown was educated at Eton and Bristol University and then became a freelance journalist in London, contributing to The Tatler, The Spectator, The Times Literary Supplement, Literary Review, the Evening Standard (as a regular columnist), The Times (notably as parliamentary sketchwriter; these columns were compiled into a book called A Life Inside) and The Sunday Times (as TV and restaurant critic). He later continued his restaurant column in The Sunday Telegraph and has contributed a weekly book review to The Mail on Sunday.

He created the characters of Bel Littlejohn, an ultra-trendy New Labour-type, in The Guardian, and Wallace Arnold, an extremely reactionary conservative, in The Independent on Sunday. In 2001, he took over Auberon Waugh's "Way of the World" in The Daily Telegraph following Waugh's death. He lost that column in December 2008. However, he is probably best known for his Diary in the fortnightly satirical magazine Private Eye, in which he adopts the persona of a celebrity or other public figure. His targets have included the Queen, Jackie Collins, Bill Clinton, Martin Amis, Harold Pinter (numerous times) and the publicist Max Clifford. A typical reference, characteristically combining viciousness and honesty in the Diary came in the purported entry for Mary Archer, married to convicted perjurer Jeffrey Archer, "I am the chairman of the Ethics Committee at Addenbrookes hospital, and well used to coming down hard on those who lie incompetently." Another typical Eye Diary mocks Martin Amis's pretensions - "Why pray, is it necessary to point out at this post-millennial juncture that Iosef Stalin is no mate of this 52-year-old novelist? Why, indeed?".

Brown also writes comedy shows such as Norman Ormal for TV (in which he appeared as a returning officer Craig Brown (II)), and his radio show This Is Craig Brown was broadcast on BBC Radio 4 in 2004. It featured comics Rory Bremner and Harry Enfield and other media personalities. He has appeared on television as a critic on BBC2's Late Review as well as in documentaries such a Russell Davies's life of Ronald Searle.

His book 1966 and All That takes its title, and some other elements, from 1066 and All That. A BBC Radio 4 adaptation followed in September 2006, in similar vein to This Is Craig Brown. The Tony Years is a comic overview of the years of Tony Blair's government, published in paperback by Ebury Press in June 2007.Brown's niece is Florence Welch of Florence and the Machine fame.