Television and film career
Hagen made his film debut in Cry in the Woods (Den som frykter ulven) in 2004. He appeared in several other films, including Erik Poppe's 2008 film Troubled Water (De usynlige). For this film he won the Kanonprisen for best performance by an actor in a leading role. A 2012 article in Filmmagasinet praising Troubled Water as a great Norwegian film gave part of the credit for its excellence to “unbelievably good acting” by Hagen and other members of the cast.
In 2008, in addition to Troubled Water, Hagen appeared in four other well-received films: Cold Lunch (Lønsj), House of Fools (De gales hus), Max Manus, and The Storm in My Heart (Jernanger).
A January 2009 profile in Aftenposten noted that he was in three different movies that were running simultaneously in Oslo cinemas – The Storm in My Heart, Max Manus, and Troubled Water – and was also rehearsing the “surrealistic comedy” Eit lykkeleg sjølvmord at Det Norske Teatret.
In the autumn of 2011 Hagen played the lead role in a four-part, 4-hour Norwegian TV mini-series, Buzz Aldrin, What Happened to You in All the Confusion? (Buzz Aldrin, hvor ble det av deg i alt mylderet?), based on the debut novel by Johan Harstad. He was nominated for a Golden Screen Award for this role.
In 2013 he starred in the family action adventure film Gåten Ragnarok.
In 2014 he played The Count in Hans Petter Moland's action thriller film In Order of Disappearance alongside Stellan Skarsgård and Bruno Ganz. He was nominated for the Amanda Award and won best actor in the Gut Buster Comedy feature category at Austin Fantastic Fest for the role.
He continued his collaboration with Hans Petter Moland in Danish thriller Conspiracy of Faith in 2016.
In early 2017 Hagen starred alongside Sven Nordin in the thriller series Valkyrien. In summer 2017 it was screened in the UK on Channel 4. He won a Golden Screen Award for his performance.
He played ice skating legend Sonja Henies' husband Niels Onstad in the biopic Sonja in 2018.
In February 2019 Amundsen, based on the life of polar explorer Roald Amundsen, opened in Norwegian cinemas. Hagen plays Roald Amundsen in the film directed by Espen Sandberg.
