The news was revealed during a panel with the "AHS" cast at Comic-Con.
Also added to the cast will be "The Normal Heart" cast member Finn Wittrock, Michael Chiklis, John Carroll Lynch and "Hunger Games" actor Wes Bentley.
It has been revealed that Paulson will portray conjoined twins Bette and Dot, with Bates, Peters, Bassett and Conroy as side show performers rescued by Lange's character. Lynch will star as the season's main villain, while Chiklis will play Bates ex-husband and Bassett's current husband.
"American Horror Story: Freak Show" will air in October.
Holed up in a seedy motel on the edge of the Mojave Desert, two former lovers unpack the deep secrets and dark desires of their tangled relationship, passionately tearing each other apart. Led by director Daniel Aukin (Back Back Back at MTC, 4,000 Miles), Tony winner Nina Arianda (Venus in Fur at MTC, Born Yesterday) and Sam Rockwell (A Behanding in Spokane, The Way Way Back) bring an explosive intensity to Sam Shepard’s (Buried Child, True West) landmark myth of the new Wild West.