In 2021, he featured in the Hulu miniseries Dopesick, for which he received an Primetime Emmy Award nomination for Outstanding Supporting Actor.

[5] He struggled in school due to dyslexia and developmental coordination disorder, but found that he loved drama, which "gave [him] a sense of purpose".

[9][better source needed] Poulter played the role of Lee Carter in the 2007 film Son of Rambow, alongside his co-star Bill Milner.

[15] The cast included a host of British talent with Leo Gregory, Neil Maskell, Liz White, Iwan Rheon, Olivia Williams, Jaime Winstone, Andy Serkis, and Sean Pertwee, and scored a perfect 100% on Rotten Tomatoes Tomatometer.

[20] In 2014 he played Fordy in the crime film Plastic, directed by Julian Gilbey and starring Ed Speleers, Alfie Allen, Sebastian De Souza and Emma Rigby.

[20] In 2015 Poulter starred as Shane in the Irish indie film Glassland,[18] directed by Gerard Barrett and co-starring Jack Reynor and Toni Collette.

[24] Poulter played Jim Bridger in the revenge-thriller The Revenant (2015), directed by Alejandro González Iñárritu, and starring Leonardo DiCaprio and Tom Hardy.

However, it was announced in June 2016 that Bill Skarsgård had been cast instead as Poulter became unavailable after the departure of its initial director Cary Fukunaga.

[18] Poulter's performance was nominated for a 2022 Primetime Emmy Award for Outstanding Supporting Actor in a Limited or Anthology Series or Movie for this role.