The following year, Madden was named one of the 100 most influential people in the world by Time, and he had supporting roles as music manager John Reid in the biopic Rocketman and Lieutenant Blake in the war film 1917.

[10][11] He worked with The Arches and the Glasgow Repertory Company during his studies; he also performed in Franz Xaver Kroetz's play Tom Fool at the Citizens Theatre.

[15] That same year, Madden played Callum McGregor in the Royal Shakespeare Company's production of Malorie Blackman's Noughts & Crosses, which ran from December 2007 to February 2008.

[16] He then starred as Mark McNulty in the National Theatre of Scotland's production of the play Be Near Me in 2009, which The Times's Benedict Nightingale described as a "skilful adaptation" of the Andrew O'Hagan novel of the same name.

[10][17] Susan Mansfield of The Scotsman wrote that Madden had caught critics' attention, reporting additional positive reviews of his performances by The Daily Telegraph and The Observer.

[30] While terrified of playing a classical fairy tale character, the actor found comfort in how audiences knew very little about the prince in the animated film and how he was able to create "a real young man.

[34][35] Michael Billington of The Guardian praised Madden's articulation of Romeo's "challenge to fate", while Variety's Matt Trueman criticised his speeches as "flat and regimented".

Writing for Digital Spy, Alex Mullane found the actor "particularly dashing" and added that his performance made the twist in the story "brutally effective".

"[42] Madden garnered acclaim and recognition for playing Sergeant David Budd, a war veteran and police officer with post-traumatic stress disorder (PTSD), in the 2018 BBC thriller series Bodyguard.

[43] Tim Goodman of The Hollywood Reporter wrote that the actor executed the role with self-possession, while The Atlantic's Sophie Gilbert observed that he conveyed Budd's "superb instincts, his cool head under fire, and his complex psyche" successfully.

[45][46] After the series finale became the most watched UK television drama episode since the beginning of current records, Netflix released Bodyguard worldwide in October 2018.

[59] Critics had mixed opinions on the series;[60][61] Daniel Fienberg of The Hollywood Reporter found Madden "adequately intense and sometimes funny in a way the insufficiently playful show needs".

[65] In an interview with British Vogue, Madden expressed pride in coming from a working class background and said that his social conscience is sparked by inequality in education and the lack of creative opportunities for working-class children in schools.