He was born on 3 May 1965 in Baglan, Neath Port Talbot.

After studying at the Welsh College of Music and Drama, he started his professional broadcasting career on BBC Radio Wales, spending six years as a DJ for the station. Working with Alan Thompson, he co-hosted the show Rave which was simulcast on Radio Wales and the fledging BBC Radio Five.

Among the sketches the pair created was Tony And Keith, the prototype for Brydon's later creation of Keith Barret.

He remained on Radio Five courtesy of the comedy show The Treatment, but became more familiar as a voice artist, from video games to adverts.

In 2000, his big break came with the screening of six, 10-minute episodes of Marion And Geoff, featuring Brydon as Keith Barret, talking of his ex-wife and her new beau. The sketches quickly gained praise, and awards: he won Best Television Comedy Newcomer at the British Comedy Awards.

Later in 2000 another series, Human Remains, aired. In each of the six episodes, Brydon and his co-star Julia Davis portrayed a different, unhappy couple in fly-on-the-wall style 'mockumentary'.

In 2001 he won the Best Television Comedy Actor at the British Comedy Awards, and had a cameo role in 24 Hour People, which starred his friend and fellow-comedian Steve Coogan. He reunited with Coogan in 2002 for another cameo in I'm Alan Partridge and once more for Cruise Of The Gods.

Marion And Geoff returned to the screens in 2003, this time expanded to half-hour episodes. Bryden took Barret on the road for a stage show entitled Making Divorce Work.

February 2004 saw the pilot for The Keith Barret Show, in which Barret is cast as the host of a chat show about relationships.

Brydon appeared several times on BBC Radio Four's I'm Sorry I Haven't A Clue, from 2006 onwards. His singing voice was described enthusiastically by host Hymphrey Lyttelton as being "Not bad". Bryden also hosted an edition of the show in Bournemouth three days before the death of Lyttelton.

He has presented Have I Got News For You and has appeared as a panellist on Radio Four's Just A Minute. He also appeared in the Bafta award winning sitcom Gavin & Stacey, playing the part of Uncle Bryn.

In 2009 Brydon was one of three guest chairmen for the new series of I'm Sorry I Haven't A Clue, following the death of former chairman Humphrey Lyttelton.