She is best known for her starring role as former demon Anya Jenkins on the supernatural drama television series Buffy the Vampire Slayer (1998–2003), which earned her a nomination for the Satellite Award for Best Cast.

In 1998, Caulfield starred in her most famous role to date, as Anya Jenkins on the WB's hit show Buffy the Vampire Slayer.

However, audiences responded well to Anya, resulting in Buffy the Vampire Slayer creator Joss Whedon's decision to add her to the main cast.

In 2003, Caulfield landed her first lead role in the horror movie Darkness Falls, which debuted at number one in the U.S. box office.

In 2012, she received critical acclaim for her guest appearance on the ABC fantasy series Once Upon a Time, as the Blind Witch from the fairytale Hansel and Gretel.