Television
Mangan's breakthrough television performance was as Adrian Mole in the six-part BBC TV show series Adrian Mole: The Cappuccino Years in 2001. That same year he appeared in Sword of Honour on Channel 4, alongside Daniel Craig.
In 2002, he appeared as Dan Moody in the I'm Alan Partridge episode "Bravealan". A scene where Alan repeatedly shouts "Dan!" at Dan from a distance in a car park, while Dan seems not to notice him, was named the second best moment from the series by Metro,
Mangan played Guy Secretan in the British sitcom Green Wing. In Channel 4's The World's Greatest Comedy Characters, Guy was voted 34th. He starred as Keith in Never Better, a British television sitcom on BBC Two. He plays a recovering alcoholic Keith Merchant and Kate Ashfield is his long-suffering wife Anita. The series was written by Fintan Ryan for World Productions.
In 2009, Free Agents, a romantic black comedy starred Mangan, Sharon Horgan and Anthony Head. Originally a pilot for Channel 4 in November 2007, the series began on 13 February 2009. It spawned a short-lived US remake, which was cancelled after just four episodes aired, although four more were later released on Hulu.
He played the title role in Dirk Gently, a British comedy detective drama TV series based on characters from the Dirk Gently novels by Douglas Adams. The series was created by Howard Overman and co-starred Darren Boyd as his sidekick Richard MacDuff. Recurring actors included Helen Baxendale as MacDuff's girlfriend Susan Harmison, Jason Watkins as Dirk's nemesis DI Gilks and Lisa Jackson as Dirk's receptionist Janice Pearce. Unlike most detective series Dirk Gently featured broadly comic touches and even some science fiction themes such as time travel and artificial intelligence. He has said that he was "bitterly upset" at the BBC's axing of the series after four episodes due to a freeze on the licence fee. The four episodes of Dirk Gently were later released on the BritBox streaming service.
He played the title role in "The Hunt for Tony Blair", a one-off episode of The Comic Strip Presents..., a British television comedy, which was first shown on Channel 4 on 14 October 2011. The 60-minute film was written by Peter Richardson and Pete Richens and presented in the style of a 1950s film noir. It stars Mangan as the former British Prime Minister Tony Blair, who is wanted for murder and on the run as a fugitive. The film received its world premiere at the Edinburgh International Television Festival in August 2011. It first aired on Channel 4 on 14 October 2011; it received a mostly positive reaction from reviewers, and was nominated for a BAFTA award (Best Comedy Programme 2012) and the British Comedy Awards (Best Comedy Drama 2011).
He appeared in Episodes, a British-American television comedy series created by David Crane and Jeffrey Klarik and produced by Hat Trick Productions. It premiered on Showtime in the United States on 9 January 2011 and on BBC Two in the UK on 10 January 2011. The show is about a British husband-and-wife comedy writing team who travel to Hollywood to remake their successful British TV series, with disastrous results. Mangan based his performance as Lincoln on his favorite shows from his youth. On 11 December 2013, it was announced that Showtime had renewed Episodes for a fourth season. Episodes has received positive reviews by critics, with many singling out Mangan, Tamsin Greig, and Matt LeBlanc's performances.
In 2018, Mangan played the lead role in a black comedy TV series Bliss, created by American comedian David Cross, which was aired on Sky One and released by the BritBox streaming service. Bliss stars Mangan as Andrew, a fraudulent travel writer, who is struggling to maintain long-term relationships with two partners, Kim (Heather Graham) and Denise (Jo Hartley), who are not aware of one another.
He co-wrote and starred in Hang Ups for Channel 4, which was adapted from the American comedy series Web Therapy. The show was first broadcast in 2018 and had an all-star cast, including David Tennant, Katherine Parkinson, Charles Dance and Richard E. Grant. It received rave reviews and was nominated for two major awards.
Also in 2018, Mangan starred in the BBC legal drama The Split opposite Nicola Walker. He reprised this role in the second series in 2020 and again in the third series in 2022.
In 2020, he co-hosted BBC Children in Need alongside Mel Giedroyc, Alex Scott and Chris Ramsey. He also served as the narrator of ITV's documentary series Who Wants to Be a Millionaire?: The Million Pound Question, which started airing in November 2020.
In May 2022, the BBC announced that Mangan would be one of the guest presenters to take over Richard Osman's role on Pointless.
In 2022, Mangan narrated the documentary and clip show 'Allo 'Allo! Forty Years of Laughter on Channel 5.
In 2023, Mangan narrated the documentaries and clips shows Keeping Up Appearances - 30 Years Of Laughs, One Foot in the Grave - 30 Years Of Laughs and Birds of a Feather - 30 Years Of Laughter for Channel 5.
In November 2023, Mangan appeared on a celebrity edition of The Weakest Link and reached the head-to-head round against Ed Byrne.
In 2024, Mangan appeared as the host of Series One of The Fortune Hotel, a reality competition series, set in a luxury hotel in the Caribbean with a prize fund of £250,000. The show went on to film Series Two the following year for ITV.
In October 2025, Mangan appeared on a special battle of the nations edition of The Weakest Link where he represented England alongside Leomie Anderson and was voted off in the fifth round by Paul Brand and Amy Macdonald.
