In 1990, Ifans presented Sdwnsh (Welsh for "Mash"), an anarchic children's quiz. In total 31 fifteen minute programmes were broadcast on S4C.

Ifans appeared in many Welsh language television programmes before embarking on his film career, as well as performing at the Royal National Theatre, London and the Royal Exchange Theatre, Manchester.

He was briefly lead vocalist of the rock band Super Furry Animals before they found national success.

His film roles include: Eyeball Paul in Kevin and Perry Go Large (2000), Nigel in The Replacements (2000), Iki in The 51st State (2001), William Dobbin in Vanity Fair (2004) and Vladis Grutas in Hannibal Rising (film) (2007). He also played Jed Parry in the film version of Ian McEwan's Enduring Love (film) and the lead role in Danny Deckchair (2003) as Danny Morgan.

In 2005, Ifans picked up a BAFTA for his critically acclaimed portrayal of iconic comedian Peter Cook in the TV film Not Only But Always. Later that year he m