Johnson attended Highgate Wood School and Performing Arts College where she was spotted by an agent in a production of Guys and Dolls in which she played the lead. The role of Vicki Fowler on the BBC's flagship soap opera EastEnders was Johnson's first television role though not her professional début, having previously appeared in numerous stage productions, including a six-month run in an acclaimed National Theatre production of Dylan Thomas' Under Milk Wood directed by Roger Michell. Johnson left EastEnders in 2004 after two years and 194 episodes, and returned to stage acting as well as embarking on career in films. In Spring 2012 Johnson played the role of a pregnant young teenager in Pramface, on BBC 3. Pramface is a comedy based on teen pregnancy. In April 2010, Johnson was cast by Warner Bros in the CW network's US TV pilot "Damn Thorpes" opposite co-star Sean Faris. In the same year she also played the lead role in the UK film Panic Button and in the Channel 4 comedy Pete Versus Life as Trish, the girlfriend of Pete's friend Ollie. In February–March 2010 she appeared in the play Slaves for the Olivier award-winning Theatre 503, London. In 2009 she played Mindy in a revival of Aunt Dan and Lemon at the Royal Court Theatre receiving good notices in the Evening Standard, The Guardian, The Times etc.[citation needed] In the same year she played the role of Helen in the horror film The Reeds. Johnson appears in the 2008 film Adulthood, the sequel to the 2006 film Kidulthood. In 2005, she played Juliet in an open air run of Romeo and Juliet at Stafford Castle and received favourable notices including in The Stage.In the same year she also appeared as the lead in the acclaimed UK tour of Henry James' Daisy Miller directed by Christopher Morahan and in the pantomime Cinderella at Stafford's Gatehouse Theatre. She played Laura in the BBC Three sitcom Pramface and is also playing the role of PJ in the second series of E4's Beaver Falls.
