Eisenberg was born in East Brunswick Township, New Jersey, the daughter of Amy and Barry Eisenberg, who ran a hospital and later became a college professor. She has two siblings: actor Jesse Eisenberg, the Academy Award-nominated star of The Social Network, and Kerry. Hallie was named after the character Hallie O'Fallon in the film All I Want for Christmas, portrayed by Thora Birch. Eisenberg attended American University, in Washington, DC.  She was brought up in a secular Jewish family.