The new FX show, from Glee's executive producers Ryan Murphy and Brad Falchuk, focuses on a family who move to a haunted house.
Harris has now landed a recurring role in the drama, The Hollywood Reporter says.
He will play R Franklin, who is described as a "sociopath killer".
Harris is currently appearing in the movie Rise of the Planet of the Apes and has recently had guest roles in shows such as The Mentalist and No Ordinary Family.
American Horror Story also stars Connie Britton, Dylan McDermott, Shelby Young, Frances Conroy, Alexandra Breckenridge, Taissa Farmiga, Evan Peters, Denis O'Hare and Jessica Lange.
The show will premiere on October 5 on FX.
> 'American Horror Story': First look in pictures