Ejiofor made his film debut in the television film Deadly Voyage (1996). He went on to become a stage actor in London. In Steven Spielberg’s Amistad, he gave support to Djimon Hounsou’s Cinque as interpreter Ensign James Covey. In 1999, he appeared in the British film GMT – Greenwich Mean Time. In 2000, he starred in Blue/Orangeat the Royal National Theatre (Cottesloe stage), and later at the Duchess Theatre. That same year, his performance as Romeo in William Shakespeare’s Romeo and Juliet was nominated for the Ian Charleson Award. Ejiofor was awarded the Jack Tinker Award for Most Promising Newcomer at the Critics’ Circle Theatre Awards in 2000. For his performance in Blue/Orange, Ejiofor received the London Evening Standard Theatre Award for Outstanding Newcomer in 2000 and a nomination for the Laurence Olivier Award for Best Supporting Actor in 2001.

Ejiofor had his first leading film role playing Nicky Burkett in Jeremy Cameron’s It Was an Accident (2000). In 2002, he starred in Dirty Pretty Things, for which he won a British Independent Film Award for best actor. In the following year, he was part of the ensemble cast of Love Actually, starred in a BBC adaptation of Chaucer’s The Knight’s Tale and also starred on the BBC series Trust. Also in 2003, he starred in the lead role of Augustus in the radio production of Rita Dove’s poetic drama “The Darker Face of the Earth”, which premiered on the BBC World Service on 23rd August of that year, marking the International Day for the Remembrance of the Slave Trade and its Abolition. He starred alongside Hilary Swank in Red Dust (2004), portraying the fictional politician Alex Mpondo of post-apartheid South Africa. He played the central role of Prince Alamayou in Peter Spafford’s radio play I Was a Stranger, broadcast on BBC Radio 4 on 17 May 2004, and he played the god Dionysus, alongside Paul Scofield’s Cadmus and Diana Rigg’s Agave, in Andrew Rissik’s play, Dionysus, based upon Euripides’ Bacchae, also broadcast by the BBC. He played Mike Terry, in the cult film Redbelt that received favourable reviews. He also received acclaim for his performance as a complex antagonist The Operative in the film Serenity (2005). Ejiofor played a revolutionary in the film Children of Men (2006).

His singing and acting performance in Kinky Boots received a Golden Globe Award and British Independent Film Award nomination. He was also nominated for the BAFTA Orange Rising Star Award in 2006, which recognizes emerging British film talent. Ejiofor’s performance in Tsunami: The Aftermath received a Golden Globe Award nomination for Best Actor – Miniseries or Television Film in 2007.