Given the important role that teachers play in supporting student mental health, it is critical teachers feel confident in their ability to fill such roles. To inform strategies intended to improve teacher confidence in supporting student mental health, a psychometrically sound tool assessing teacher school mental health self-efficacy is needed. The current article details the initial development and psychometric functioning of the school mental health self-efficacy teacher survey (SMH-SETS). A component of the development included Rasch analysis of pilot data to provide a psychometric appraisal of the SMH-SETS functioning and initial psychometric evidence. Results suggest the SMH-SETS exhibits strong psychometric properties and can be used to measure school mental health self-efficacy, track self-efficacy over time, and inform training and professional development.