He first appeared in the
BBC Wales drama
Crash in 2009, portraying Dylan. The following year, he appeared in the daytime medical soap opera
Doctors in a week-long storyline entitled "Master of the Universe," in which he played the lead role of Lewis Cutler. The episodes were then nominated for "Best Single Episode" and "Spectacular Scene of the Year" at the
British Soap Awards in 2010. Also in 2010, he appeared in both
Pen Talar and
The Indian Doctor, and the film
Bright Lights. In 2012, he earned the role of Private Keenan in
Privates, a mini-television series about conscripts in the
National Service set in the 1960s, for which he shaved his head. From 2012 to 2016, he played the role of
Dorian Gray in
Big Finish Productions' audio series
The Confessions Of Dorian Gray. He has also written one of the episodes, "The Mayfair Monster," released in October 2013, and the audio play,
HMS Surprise for the
Bernice Summerfield box set
New Frontiers, which was released in April 2013. From 6 December 2013, Vlahos appeared in ''
Fortune's Fool'' at
The Old Vic.
Mike Poulton's adaptation of
Turgenev's play was directed by
Lucy Bailey, in a new production which starred
Iain Glen and
Richard McCabe. In July 2015, it was announced that he would be playing Bertie Potts in the mini audiobook series
The Diary of River Song set in the
Doctor Who universe, alongside
Alex Kingston. Since 2015, he portrayed
Louis XIV's brother,
Philippe I, Duke of Orléans, in the Franco-Canadian historical television series
Versailles, about life at the French court, The first series premiered in November 2015. Series 2 was filmed in early 2016 and explores the lighter side to Philippe, the first time for Vlahos to portray a rather light-hearted character for an extended period of time. In March 2018, Vlahos confirmed that the third season would also be
Versailles' final one. In the 2016 docudrama
Barbarians Rising, a global co-production for
The History Channel, Vlahos played the Roman emperor
Valentinian in one episode. He also portrayed the Romanian philosopher and mathematician
Maurice Solovine in one episode of
Genius,
National Geographic Channel's first scripted series. From 11 February to 11 March 2017 in London, Vlahos starred
La Ronde, directed by Max Gill, which was a modernised, gender-neutral version of the play by
Arthur Schnitzler. A cast of four played the 10 characters randomly selected onstage every night by a roulette wheel. In summer 2018, Vlahos played Romeo in
Romeo and Juliet, and Catesby in
Richard III at the Shakespeare's Rose Theatre in York, before returning to the
Park Theatre in London to portray Captain Hook and Mr Darling in a stage production of
Peter Pan. Vlahos played the artist, Charles Lockhart, in the PBS show
Sanditon which aired in 2022–2023. He will be appearing in the
Netflix movie,
Irish Wish, in 2024. ==Personal life==