Conroy will play a different character than she did in Season 1 of the series.
The first season was set in a haunted house in California during modern times, while the second will take place in an East Coast psychiatric hospital in the 1960s.
"Thrilled to announce Emmy nominee Frances Conroy is returning to AHS," Murphy tweeted Wednesday. "Devils and angels this year...Frannie plays the ultimate angel."
"It would be dark, but it would be great," Conroy recently told The Hollywood Reporter about the possibility of returning for Season 2 of the show. "It would be so interesting to jump into another world if they put me on for an episode."
Season 2 is to premiere Oct. 17.