Redmayne made his professional stage debut for Shakespeare's Globe Theatre in Twelfth Night at the Middle Temple Hall in 2002. He won the award for Outstanding Newcomer at the 50th Evening Standard Theatre Awards (2004) for his performance in Edward Albee's The Goat, or Who is Sylvia?, and the award for Best Newcomer at the Critics' Circle Theatre Awards in 2005.

His screen credits include the BBC miniseries Tess Of The D'Urbervilles and films such as The Good Shepherd, Powder Blue,Savage Grace, The Other Boleyn Girl and Glorious 39. So far, he has starred in three films based on the Tudor period.
Redmayne is attached to star in the film adaptation of Ruardidh Nicoll's White Male Heart.
His most recent stage credits include Now or Later by Christopher Shinn at the Royal Court Theatre, London. The show ran from the 3 September to 18 October 2008.
In 2009 Redmayne appeared in John Logan's new play Red at the Donmar Warehouse, for which he won the 2010 Olivier Award for Best Actor in a Supporting Role. He is reprising his role in Red at the John Golden Theatre in its 15-week run from 11 March to 27 June 2010, and won the 2010 Tony Award for Best Performance by a Featured Actor in a Play.
Redmayne's 2009 Sundance hit The Yellow Handkerchief was released in theaters on 26 February 2010 by Samuel Goldwyn Films.
Redmayne won the American Theater Wing Best Actor award for his portrayal of Ken in the Broadway production of Red (play) on June 13, 2010 at the Tony Awards in New York City.