Emilia’s film debut was in Roman Polanski's film The Pianist. Her other notable films include the Italian–French–British romance-drama film The Soul Keeper (2002), for which she won the Flaiano Film Award for Best Actress; the drama film The Republic of Love (2003); the comedy-drama film Things to Do Before You're 30 (2005); the black comedy Keeping Mum (2005); the romantic comedy-drama film Cashback (2006); the drama Flashbacks of a Fool (2008); the drama film Ways to live Forever (2010); the drama-thriller A Thousand Kisses Deep (2011); and the fantasy-horror drama film Dorian Gray (2009).

Her television roles include BBC drama Pride and Prejudice (1995), the PBS British/German television serial Rebecca (1997), ITV Granada's Henry VIII (2003), BBC's Gunpowder, Treason & Plot (2004), BBC mini series The Virgin Queen (2005) and the ITV crime drama series Fallen Angel (2007). She also appeared as Morgause in the BBC's Merlin and Sky’s Delicious (2016).

Emilia stars as Dr. Nikki Alexander on BBC crime drama Silent Witness, having joined the cast in 2004.

Plays include Les Liaisons Dangereuses with Jared Harris and Coriolanus with Ralph Fiennes.