Dillane made his acting debut with a minor role in the film titled Welcome to Sarajevo in 1997. He was just six years old then. He garnered worldwide fame after portraying the role of Tom Riddle in the Harry Potter franchise film called Harry Potter and the Half-Blood Prince in 2009.
After clearing his A-level examinations, Dillane was embraced to the RADA (Royal Academy of Dramatic Art) and finally obtained his graduation degree in Bachelor of Arts in Acting from there in 2013. Albeit of the school rules stating that students who are already actors are not allowed to accept professional acting jobs during the duration of the course. Dillane in the special case was allowed to play the role of James Papadopoulos in the independent film directed by Marcus Markou called Papadopoulos & Sons in 2011.
After completion of his studies from the Royal Academy of Dramatic Arts, Dillane since then has worked on various projects. In a play directed by Simon Godwin called Candida, he was cast in lead role in 2013. Come 2014 and Dillane essayed the role of Keyes in the film 'Viena and the Fantomes'. In this film, he was cast alongside Dakota Fanning. Dillane portrayed the role of Shugs in the Netflix 2015 series called Sense8 which was directed by the noted director Wachowskis. Dillane’s career took new highs after he was finalised to play the lead role of Paul in the adaptation of Peter Goldsworthy's best-selling novel named Maestro.