Mental health professionals can support LGBT youth in schools by applying affirmative-counseling practices to prevent stressors that affect mental health. Little is known about the use of affirmative practices in schools among school social workers and psychologists. A modified version of the Lesbian, Gay, and Bisexual Affirmative Counseling Self-Efficacy Inventory—Short Form (LGB-CSI-SF) was administered to school mental health professionals [i.e., school social workers (n = 62) and school psychologists (n = 39)] in South Florida. The modified LGB-CSI-SF is reliable and may be used in schools with mental health professionals. The modified LGB-CSI-SF can assess the need for affirmative counseling trainings. [ABSTRACT FROM AUTHOR]