He then landed the part of 9 year-old Tom Riddle in Harry Potter and the Half-Blood Prince out of thousands of young actors who auditioned for the role.

[8] Yates described Fiennes Tiffin as "very focused and disciplined"[9] and said he "got the corners and dark moods and odd spirit of the character",[7] as well as having a "wonderful haunted quality that seemed to bring Tom Riddle alive on-screen for us".

[9] After Harry Potter, Fiennes Tiffin then landed British television roles in Private Peaceful (2012) and Safe (2018), as well as a short independent film called Possession with Intent to Supply (2016).

[14] In addition to acting, Fiennes Tiffin has modelled for Dolce & Gabbana, Dior, H&M, Hugo Boss, Fendi, Oliver Peoples, Superdry,[15] Ferragamo,[16] and David Yurman.

[17] His upcoming projects include The Climb, a film based on the 2013 Greenpeace protest where activists illegally scaled The Shard in London in protest against Arctic oil drilling,[18] Mr. Smith, a thriller in which Fiennes Tiffin's character returns to an Irish port to solve his brother's sadistic murder (written and directed by Declan O'Dwyer),[19] Above the Below, a thriller where Fiennes Tiffin plays an idealistic astronaut on a mission of survival following a botched re-entry to earth (starring opposite Idris Elba who plays the mission's commander),[20] Picture This (upcoming film), and Making Noise.