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 has also appeared on Irish television, having starred in the RTÉ One drama The Clinic and the drama Showbands'' alongside
Kerry Katona. He has appeared in
How to Lose Friends & Alienate People in a minor role. He has also had roles in a number of films, including the 2005 film
Festival where he played stand-up comedian Tommy O'Dwyer, a role for which he won a Scottish
BAFTA award, and a small role in
Vera Drake. He appears in
Frequently Asked Questions About Time Travel, a comedy sci-fiction film with
Marc Wootton,
Dean Lennox Kelly, and
Anna Faris. He played Liam in the 2007 German film ''''. He starred in the 2009 film
The Boat That Rocked, inspired by the story of offshore pirate broadcasters
Radio Caroline, which was released in Canada and the U.S. as
Pirate Radio. O'Dowd plays Simon, the station's breakfast DJ. "The breakfast jock on Radio Caroline at the time was Tony Blackburn, so there's definitely an element of him in it," O'Dowd says of his character. "And then I called in different Irish DJs that would have been contemporaries of Tony Blackburn at the time, a guy called
Larry Gogan and a couple of other people." 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. O'Dowd had a supporting role in
This Is 40. He described "fighting over
Megan Fox in a pool" during filming as "one of the most fun things I've ever done". He played Dave in Wayne Blair's 2012 debut feature Australian musical
The Sapphires. Based on a popular stage show, it was shot across Australia and Vietnam and produced by
Goalpost Australia. He is to write and
executive produce a new American comedy series called
Big Men, after NBC won the bidding war for it. He co-wrote
Moone Boy, a series based on his childhood, for
Sky 1. It was filmed in his hometown of
Boyle. Segments of it ran from 2012 to 2015. O'Dowd has also co-written some books based on the series:
Moone Boy: The Blunder Years (published May 2015),
Moone Boy: The Fish Detective (October 2015),
Moone Boy: The Notion Potion (September 2017), and an activity book,
Moone Boy: The Marvellous Activity Manual (May 2017). From April to July 2014, O'Dowd starred in the Broadway revival of
Of Mice and Men, directed by
Anna D. Shapiro and co-starring
James Franco and
Leighton Meester, for which O'Dowd was nominated for a
Drama Desk and
Tony Award for Best Actor in a Play. He starred as a Catholic school teacher in the 2014 film
St. Vincent with Bill Murray and Melissa McCarthy. He was also the narrator for the 2014 RTÉ documentary
Man on Bridge. From 2017 to 2019, O'Dowd played the lead role in three seasons of the
MGM+ television show
Get Shorty, created by
Davey Holmes and co-starring
Ray Romano, for which O'Dowd received a nomination for Best Actor in a Leading Role from the 2018
IFTA Film & Drama Awards. In 2022, O'Dowd played Philip in the
Netflix film
Slumberland alongside
Jason Momoa,
Kyle Chandler and young actress Marlow Barkley. O’Dowd created and starred in the television series
Small Town, Big Story, which premiered 27 February 2025 on
Sky. ==Personal life==