He received wide attention as Roy Trenneman, one of the lead characters in the Channel 4 comedy The IT Crowd, which ran for four series between 2006 and 2010.

He has also starred in several films, including Gulliver's Travels (2010), Bridesmaids, Friends with Kids (both 2011), Cuban Fury (2014), Miss Peregrine's Home for Peculiar Children (2016) and The Cloverfield Paradox (2018).

[8] He studied politics and sociology at University College Dublin (UCD), and subsequently attended the London Academy of Music and Dramatic Art (leaving before graduating after 18 months).

[10] O'Dowd starred in the UK in Channel 4's comedy The IT Crowd, BBC Two's Roman's Empire, Red Cap, and the award-winning documentary-drama The Year London Blew Up.

He appears in Frequently Asked Questions About Time Travel, a comedy sci-fiction film with Marc Wootton, Dean Lennox Kelly, and Anna Faris.

"[11] O'Dowd appeared in the 2010 film Dinner for Schmucks, an American version of the French farce Le Dîner de Cons.

[12] He also appeared on panel show Never Mind the Buzzcocks (season 21, episode 11), and starred in an ITV2 comedy series entitled FM.

In 2010, he took part in Little Crackers, writing and directing a short film loosely based on his own childhood and Christmas in his family home from 1984 to 1988.

In April 2011, he starred in the BBC adaptation of The Crimson Petal and the White as William Rackham, and in the May 2011 release Bridesmaids as Officer Nathan Rhodes.

[18][19] He is to write and executive produce a new American comedy series called Big Men,[20] after NBC won the bidding war for it.

[25] In 2022 Chris played Philip in the Netflix film Slumberland alongside Jason Momoa, Kyle Chandler and young actress Marlow Barkley.

[26] O’Dowd created and will star in the upcoming television series Small Town, Big Story, which premieres February 27th 2025 on Sky.