Claire Julia Hawes was born into the family of a taxi driver, the youngest of four children.

From 2001 to 2004, Keeley was married to cartoonist Spencer McCallum. In this marriage, Hawes gave birth to her first child, a son, Myles McCallum (born in April 2000).

Since 8 October 2004, Keeley has been married for the second time to actor Matthew Macfadyen, whom she had been dating for two years before their wedding. In this marriage, Hawes gave birth to her second and third children: a daughter, Maggie Macfadyen (born in December 2004), and a son, Ralph Macfadyen (born in September 2006).