Eliza Bennett was born in Reading, Berkshire, England. She started acting at a young age when she appeared in stage productions at school, and even appeared professionally in the film Nanny McPhee (2005), which also starred Colin Firth and Emma Thompson. Soon after she portrayed the role of Nora in Marple: By the Pricking of My Thumbs (2006).

Eliza played Young Anne in the 2006 film Victims, and was Emily in The Contractor (2006) with Wesley Snipes. She auditioned for the role of Meggie Folchart in the film Inkheart, based on the novel by Cornelia Funke. Bennett beat out hundreds of girls for the coveted part, and in early 2007 was in Italy filming the movie with Brendan Fraser, Paul Bettany and Helen Mirren.

Eliza also performed a song for Inkheart's soundtrack, called «My Declaration», originally written and performed by Tom Baxter.

She currently attends Italia Conti Academy of Theatre Arts.