In June 2010 it was announced Barlett would be appearing as Hannah Pitt in Signature Theatre Company's 20th-anniversary production of Tony Kushner's Angels in America. She also portrayed Bridget Kearns in Shutter Island in 2010.
In 2013, she portrayed Dr. Miranda Crump in American Horror Story's second season, Asylum, and later that year returned for the third season, Coven, portraying Cecily Pembroke.
She starred in the 2014 film H., for which she was nominated for the Independent Spirit Award for Best Supporting Female in 2016.
