[1] O'Hanlon moved into straight acting alongside Emma Fielding and Beth Goddard in the ITV comedy-drama Big Bad World, which aired for two series in summer 1999 and winter 2001.

[1] He also played a minor role in The Butcher Boy as Joe's (Francie's best friend) father, and appeared in an episode of the original Whose Line is it Anyway?.

He appeared in the 2005 BBC One sitcom Blessed, written by Ben Elton; at the 2005 British Comedy Awards, it was publicly slated by Jonathan Ross, albeit in jest.

[5] Towards the end of 2005, he played an eccentric Scottish character, Coconut Tam, in the family based film, The Adventures of Greyfriars Bobby.

In 2006, O'Hanlon wrote and presented an RTÉ television series called Leagues Apart, which saw him investigate the biggest and most passionate football rivalries in a number of European countries.

He appeared in the Doctor Who episode "Gridlock", broadcast on 14 April 2007, in which he played a catlike creature named Thomas Kincade Brannigan.

[6] O'Hanlon appears in series 3 of the TV show Skins,[1] playing Naomi Campbell (Lily Loveless)'s politics teacher named Kieran, who attempted to kiss her.

O'Hanlon plays the lead role in Irish comedy television programme Val Falvey, TD on RTÉ One.

In February 2011, O'Hanlon returned to the Gate Theatre, Dublin starring in the Irish premiere of Christopher Hampton's translation of Yasmina Reza's God of Carnage, alongside Maura Tierney.

In 2023, he played Uncle Jack in the National Theatre's production of Dancing at Lughnasa by Brian Friel, alongside Siobhan McSweeney and Tom Vaughan-Lawlor.