He is known for his roles as Cyril Gray in Nanny McPhee and the Big Bang (2010), Jake Farley in Summer in Transylvania(2010), and Lommy Greenhands in Game of Thrones.

He also appeared in a recurring role on the television series Da Vinci's Demons, as Nico Machiavelli (2013–2015).

Vlahos' parents work in commercial partnership together, they own and operate the Cyberdog shop in Camden Market; a fashion, accessory, and toy retailer they founded together in 1994.

[4] In the summer of 2008, at the age of 13, Vlahos wrote and performed his own material at the Edinburgh Festival Fringe.

In December of that year, he was recruited to review Christmas pantomimes for The Guardian newspaper and website.