Young Sherlock Season 1 launched all eight episodes on Amazon Prime Video on March 4, 2026. The series stars Hero Fiennes Tiffin as a raw, 19-year-old Sherlock Holmes navigating Oxford University and his first murder case. Created by Matthew Parkhill and directed by Guy Ritchie, it is based on Andrew Lane’s YA novel series and pulls together one of the most recognizable ensemble casts of any 2026 streaming debut.
This is not a recap post written from a trailer. The cast details here come from production reporting, premiere interviews, and episode-by-episode context that most roundups skip entirely. If you have watched the show and want to understand who each actor is and why their casting matters, this guide covers every major role with the specificity that the performances actually deserve.
Who Plays Sherlock Holmes in Young Sherlock?
Hero Fiennes Tiffin plays Sherlock Holmes as a disgraced 19-year-old working as a scout, essentially a servant, at Oxford rather than a student. Most people recognize him from the After film franchise and from playing young Tom Riddle in Harry Potter and the Half-Blood Prince back in 2009. He also worked with Ritchie on The Ministry of Ungentlemanly Warfare in 2024, which made him the director’s first choice for this role.
Who Plays Moriarty in Young Sherlock?
Dónal Finn plays James Moriarty, and critics widely agree he steals every scene he is in. Born in County Cork, Ireland, Finn trained at the London Academy of Music and Dramatic Art. He replaced Barney Harris as Mat Cauthon in The Wheel of Time starting Season 2, and currently plays Orpheus in the West End production of Hadestown. His Moriarty is a scholarship student, not yet a villain, which makes the dynamic genuinely compelling.
Who Plays Princess Gulun Shou’an in Young Sherlock?
Zine Tseng plays Princess Gulun Shou’an, also known as Xiao Wei, a character functioning as the show’s version of Irene Adler. Tseng broke out internationally with her role as Ye Wenjie in Netflix’s 3 Body Problem, winning the 2024 Gotham TV Award for Outstanding Performance in a Drama Series. A major mid-season twist reveals her character is not actually a princess but is pursuing revenge against Oxford professors who destroyed her village with a lethal virus.
Who Plays Mycroft Holmes in Young Sherlock?
Max Irons plays Mycroft Holmes, Sherlock’s older brother and the one pulling strings at the Foreign Office to keep his sibling out of prison. Irons is the son of Jeremy Irons and has built a strong career through MGM’s espionage thriller Condor (2018 to 2020), The Little Drummer Girl (2018), and Miss Austen (2025). Reviewers have called this one of his best roles to date, noting he plays Mycroft’s English repression with precision and real emotional undertow.
Who Plays Silas Holmes, Sherlock’s Father?
Joseph Fiennes plays Silas Holmes, Sherlock’s father and the season’s central villain, a Machiavellian patriarch with plans involving chemical warfare. What makes this casting uniquely interesting is that Joseph Fiennes is Hero Fiennes Tiffin’s real-life maternal uncle, making this their first time acting together on screen. Joseph is best known for The Handmaid’s Tale, Shakespeare in Love, and Elizabeth, and he received Emmy and SAG nominations for the former.
Who Plays Cordelia Holmes, Sherlock’s Mother?
Natascha McElhone plays Cordelia Holmes, a perceptive and emotionally intelligent woman confined to a sanatorium following the death of her daughter Beatrice. McElhone is a seasoned dramatic actress with a career stretching back to The Truman Show in 1998. More recently she appeared in The Crown in 2022 and starred in Halo from 2022 to 2024. Her role here is smaller but her scenes with both Irons and Fiennes Tiffin carry significant emotional weight in the back half of the season.
Who Plays Sir Bucephalus Hodge in Young Sherlock?
Colin Firth plays Sir Bucephalus Hodge, the Oxford benefactor whose death sets the entire murder mystery in motion. Firth won the Academy Award, Golden Globe, and BAFTA for The King’s Speech in 2010 and received a Golden Globe nomination for HBO’s The Staircase in 2022. His most recent credit before this was Sky’s Lockerbie: A Search For Truth in 2025. Multiple reviews single him out as one of the season’s highlights, describing his oily entitled performance as genuinely fun.
Who Plays Constable Lestrade in Young Sherlock?
Scott Reid plays Constable Lestrade, depicted here early in his career as an ambitious lower-ranking officer hungry for advancement long before he becomes the Scotland Yard inspector audiences know from later Holmes adaptations. Reid is a progressively more recognized British TV actor, and this role represents his highest-profile casting to date. The character exists on the edges of the main plot in Season 1, but his presence clearly sets up a longer arc should the show get a second season.
Who Plays Esad Kasgarli in Young Sherlock?
Numan Acar plays Esad Kasgarli, one of the more textured supporting roles in the season. Acar is a prominent Turkish actor with international credits including Spider-Man: No Way Home and the 2019 live-action Aladdin, where he played Hakim. He also had a recurring role in the Showtime series Homeland. His casting in Young Sherlock continues a trend of the show’s producers reaching for genuinely credentialed international talent rather than filling supporting slots with lesser-known faces.
Does Young Sherlock Have Good Reviews?
The show holds an 83% on Rotten Tomatoes based on 45 reviews. The Metacritic score sits at 66 out of 100 from 17 critics, landing in “generally favorable” territory. The critical consensus points to Guy Ritchie’s signature kinetic style as the glue holding the series together. Finn’s Moriarty and the Holmes-Moriarty dynamic receive the strongest praise across reviews, while some critics note the plotting spreads itself too thin across its globe-trotting conspiracy in the second half.
Young Sherlock Is Worth Knowing Before Season 2 Talk Begins
The trailer for Young Sherlock set a new record for the most watched Amazon Prime Series trailer in its first seven days after releasing February 5, 2026, which signals that Prime Video has a genuine hit on its hands regardless of the mixed critical reception. Filming wrapped in late February 2025 after shooting in Bristol, Cardiff, Jerez, Cadiz, and Seville. The real-life uncle-nephew casting of the Fiennes family, the Rotten Tomatoes score, and the Wheel of Time to Hadestown career arc of Donal Finn are the details most casual recaps skip. Knowing the cast at this level means you are already ahead of the conversation if a Season 2 announcement lands.
