Tara is the daughter of Sarah Fitzgerald and Michael Callaby. She has two sisters, called Arabella and Bianca. The Fitzgeralds have an acting tradition, beginning with Tara's great-aunt, the Irish movie star Geraldine Fitzgerald (1913-2005).
Tara grew up in the Bahamas (where her grandfather, David Fitzgerald, was a lawyer), Glasgow, Dublin, Stratford-on-Avon and London. She left school at sixteen, then trained for an acting career at London's Drama Centre.
From July 2001 to May 2003, Tara was married to John Sharian.