It's not clear who the actress will be playing, but she will act in scenes opposite returning co-star Sarah Paulson in the upcoming second season, reports TV Line.
The Carnivàle actress, who also starred in The Faculty and Girl, Interrupted, will appear in multiple episodes.
The new season will take place in the '60s at an asylum for the criminally insane run by Jessica Lange, who also appeared in the show's freshman run.
American Horror Story recently cast All My Children star Mark Consuelos as one of the asylum's patients, named Spivey.
Other stars who have previously joined the series include Adam Levine, Chloe Sevigny, Zachary Quinto and Joseph Fiennes.
