Ardal began his show business career while at Dublin University where he and his friends would hire themselves out as wacky after-dinner speakers. After this he got together with two fellow university students, Barry Murphy and Kevin Gildea, to form the comedy troupe, Mr Trellis. They established The Comedy Cellar, Ireland's first alternative comedy club in the upstairs room of The International Bar, Dublin. In 1994 Ardal and Kevin went to London to enter The Comedy Newcomer Of The Year competition at The Hackney Empire which Ardal won.

It was while performing his stand-up routines in London that Ardal was spotted by Graham Lineham, who was casting for a new Channel 4 sitcom entitled Father Ted. Ardal won the role of the innocent but extremely daft, Father Dougal McGuire and his career has gone from strength to strength since. As well as Father Ted, Ardal has also starred in the TV series My Hero and Big Bad World. He has hosted a series of The Stand Up Show on BBC1 and made guest appearances in shows such as Whose Line Is It Anyway?, Shooting Stars and recently he hosted The 100 Greatest TV Characters on Channel 4.

Ardal has also acted on the big screen in 'The Butcher Boy' (1997) and was an extra in 'My Left Foot', in which you can apparently see his right ear in the church scene! More recently Ardal went to Hollywood to make a short film entitled 'Another Bobby O'Hara Story' in the title role as a gangster! He also voiced the reindeer in the comic relief Christmas Day animation special 'Robbie The Reindeer- Hooves Of Fire'. He also appeared in 'Flying Saucer Rock 'n' Roll' in 1997.

Earlier this year Ardal was also invited to New York to film his own comedy special for the comedy central TV network.