School professionals who work with students with autism spectrum disorder (ASD) play a significant role in the academic experiences of these students, but some evidence suggests that teachers of students with ASD experience a high risk of burnout. Research has begun to examine factors that ameliorate or prevent teacher burnout, including teacher training and teacher self-efficacy, or teachers’ beliefs regarding their abilities to bring about positive outcomes for their students. The present study examined variables associated with the self-efficacy of school professionals for working with students with ASD, including knowledge about ASD, prior experience working with students with ASD, and prior training in ASD and evidence-based practices. A second goal of the present study was to investigate the impact of training on ASD and evidence-based practices on school professionals’ knowledge and self-efficacy related to working with students with ASD. In particular, the participants received training on the Prevent–Teach–Reinforce model. Results of the present study suggested the importance of training to school professionals’ self-efficacy, highlighting the need for continued efforts to provide quality training to individuals who work with students with ASD.