Hawes has appeared in several successful adaptations of classic and modern novels, including Tipping the Velvet (2002), Wives and Daughters (1999), Our Mutual Friend (1998), and Under the Greenwood Tree (2005). She has also appeared in films such as The Avengers (1998), The Last September, Complicity (2000) and A Cock and Bull Story (2006), and three music videos, for the singles "Saturday Night" by Suede, Common People by Pulp and "She's a Star" by James.

On 23 February 2006, it was revealed that Hawes had replaced Jonell Elliott as the voice of Lara Croft. She voiced the role of Eidos Interactive's globe-trotting adventurer in Lara Croft Tomb Raider: Legend, now under the reins of Crystal Dynamics. She reprised her role in the 2007 remake of the original Tomb Raider game, Lara Croft Tomb Raider: Anniversary. In December 2007 it was confirmed that Hawes will continue providing Lara's voice in Tomb Raider: Underworld.

She was also cast as Jane in the 2007 comedy Death at a Funeral, where she plays the supportive wife of her off-screen husband Matthew Macfadyen whose father's funeral turns into a disaster.

In 2008, Hawes starred in the film Flashbacks of a Fool with Daniel Craig where she plays the adult version of his younger sister, Jessie. In September 2008, she will begin shooting the second series of the smash-hit television show Ashes to Ashes, in which she has the lead female role of Alex Drake. Glamour Magazine presented Hawes with 'Best Television Actress' award at the Woman of the Year Awards in 2008 for her role as Alex Drake in Ashes to Ashes.

She is nominated for a TV Choice awards for Ashes to Ashes.