Mental health parity legislation can improve mental health outcomes. U.S. state legislators determine whether state parity laws are adopted, making it critical to assess factors affecting policy support. This study examines the prevalence and demographic correlates of legislators’ support for state parity laws for four mental illnesses- major depression disorder, post-traumatic stress disorder (PTSD), schizophrenia, and anorexia/bulimia. Using a 2017 cross-sectional survey of 475 U.S. legislators, we conducted bivariate analyses and multivariate logistic regression. Support for parity was highest for schizophrenia (57%), PTSD (55%), and major depression (53%) and lowest for anorexia/bulimia (40%). Support for parity was generally higher among females, more liberal legislators, legislators in the Northeast region of the country, and those who had previously sought treatment for mental illness. These findings highlight the importance of better disseminating evidence about anorexia/bulimia and can inform dissemination efforts about mental health parity laws to state legislators.