Young Sherlock cast: Hero Fiennes Tiffin and Dónal Finn star
Fiennes Tiffin stars alongside his real-life uncle, Joseph Fiennes.
New Prime Video series Young Sherlock sees director Guy Ritchie return to the world of Arthur Conan Doyle's detective, this time charting his younger day.
The series sees Hero Fiennes Tiffin in the role of a young Sherlock Holmes, taking on his first ever case which unravels a globe-trotting conspiracy.
Also in the cast are Dónal Finn, Max Irons, Zine Tseng, Natascha McElhone and Colin Firth, while Fiennes Tiffin's real life uncle Joseph Fiennes plays Sherlock's father, Silas.
Want to see this content?
To show this content, we need your permission to allow Google reCAPTCHA and its required purposes to load content on this page.
Read on for everything you need to know about the cast of Young Sherlock.
Young Sherlock cast guide: Full list of actors
Here are the main cast members and characters in Young Sherlock – read on below for more info about who they are and where you've seen the actors before.
- Hero Fiennes Tiffin as Sherlock Holmes
- Dónal Finn as James Moriarty
- Max Irons as Mycroft Holmes
- Zine Tseng as Princess Gulun Shou'an
- Joseph Fiennes as Silas Holmes
- Natascha McElhone as Cordelia Holmes
- Colin Firth as Sir Bucephalus Hodge
Hero Fiennes Tiffin plays Sherlock Holmes
Who is Sherlock Holmes? Sherlock is a young man struggling to find his place in the world, but who has an exceptional intellect and deductive powers. He will one day become the iconic detective.
Where have I seen Hero Fiennes Tiffin? Fiennes Tiffin has had roles in films including Harry Potter and the Half-Blood Prince, The Woman King, The Ministry of Ungentlemanly Warfare and the After film series, as well as series such as Safe and Cleaning Up. He is the nephew of actors Ralph and Joseph Fiennes.
Dónal Finn plays James Moriarty
Who is James Moriarty? James is student at Oxford who matches Sherlock in intellect. The pair become close friends, but we know they will one day be the ultimate adversaries.
Where have I seen Dónal Finn? Finn has had roles in films including How to Build a Girl, Fantastic Beasts: The Secrets of Dumbledore and Four Letters of Love, as well as series such as The Witcher, SAS Rogue Heroes and The Wheel of Time.
Max Irons plays Mycroft Holmes
Who is Mycroft Holmes? Mycroft is Sherlock's older brother, who works for the Foreign Office.
Where have I seen Max Irons? Irons has had roles in films including Dorian Gray, The Host, The Riot Club, Woman in Gold, The Wife and Terminal, as well as series such as The White Queen, The Little Drummer Girl, Condor and Miss Austen.
Zine Tseng plays Princess Gulun Shou'an
Who is Princess Gulun Shou'an? Gulun is a Chinese Princess who is attending Oxford University.
Where have I seen Zine Tseng? Tseng previously had a key role in the Netflix series 3 Body Problem.
Joseph Fiennes plays Silas Holmes
Who is Silas Holmes? Silas is Sherlock and Mycroft's father, a scientist and explorer.
Where have I seen Joseph Fiennes? Fiennes is known for his roles in films including Elizabeth, Shakespeare in Love, Enemy at the Gates, Killing Me Softly and Hercules, as well as series such as Flashforward, Camelot, American Horror Story, The Handmaid's Tale and Prisoner 951. He will soon be seen reprising his stage role as Gareth Southgate in the BBC's adaptation of Dear England.
Natascha McElhone plays Cordelia Holmes
Who is Cordelia Holmes? Cordelia is Sherlock and Mycroft's mother, who has had struggles with her mental health and is in an asylum.
Where have I seen Natascha McElhone? McElhone is known for her roles in films including Mrs Dalloway, The Truman Show, Killing Me Softly and The Other Boleyn Girl, as well as series such as Californication, Designated Survivor, The First, The Crown, Halo and Hotel Portofino.
Colin Firth plays Sir Bucephalus Hodge
Who is Sir Bucephalus Hodge? Bucephalus is a senior figure at Oxford University.
Where have I seen Colin Firth? Firth is known for his roles in films including The English Patient, Shakespeare in Love, the Bridget Jones franchise, The Importance of Being Earnest, Love Actually, Nanny McPhee, Mamma Mia!, A Single Man, The King's Speech, Tinker Tailer Soldier Spy, The Railway Man, Kingsman: The Secret Service, The Mercy, 1917, Mary Poppins Returns and Operation Mincemeat, as well as series such as Pride and Prejudice, The Staircase and Lockerbie: A Search for Truth.
Young Sherlock will premiere on Prime Video on 4 March 2026 – try Amazon Prime Video for free for 30 days. Plus, read our guides to the best Amazon Prime series and the best movies on Amazon Prime.
Add Young Sherlock to your watchlist on the Radio Times: What to Watch app – download now for daily TV recommendations, features and more.
Check out more of our Drama coverage or visit our TV Guide and Streaming Guide to find out what's on. For more TV recommendations and reviews, listen to The Radio Times Podcast.
Authors
James Hibbs is a Drama Writer for Radio Times, covering programmes across both streaming platforms and linear channels. He previously worked in PR, first for a B2B agency and subsequently for international TV production company Fremantle. He possesses a BA in English and Theatre Studies and an NCTJ Level 5 Diploma in Journalism.
