He is also known for his roles in Coronation Street (2001–2003) as Adam Barlow and the films Shell (2012), In Fear (2013), Not Another Happy Ending (2013), Lost River (2014), and Overlord (2018).

And still after that I said, look, I'd really like to pursue acting.De Caestecker made his professional acting debut in the BBC short film Billy and Zorba at the age of nine.

The following year he first appeared as Adam Barlow in Coronation Street, the UK's longest-running and most-watched TV soap opera.

He played the lead in BAFTA-winning BBC series The Fades and Young James Herriot; the latter earned him a nomination for a BAFTA Scotland for Best Actor/Actress – Television.

That same year, De Caestecker appeared in Filth ("I'm a big fan of Irvine Welsh and [...] I got to play all my scenes with James McAvoy which meant a lot to me")[12] and Not Another Happy Ending; the latter earned him his second BAFTA Scotland nomination, this time in the Best Actor/Actress – Film category.

character was animated for an episode of Disney XD's Ultimate Spider-Man vs. the Sinister 6, to which the actor lent his voice.

[16] In 2014, De Caestecker played the lead role in Ryan Gosling's directorial debut Lost River.

[19] In 2020, De Caestecker starred as young Douglas Petersen in BBC One's four-part miniseries Us, based on David Nicholls' novel of the same name.

[21] Fresh from wrapping up work on Roadkill, De Caestecker filmed horror short Upstairs.