Teachers of students with emotional and behavioral disorders face unique challenges in the classroom that are often not addressed in teacher preparation, which may result in diminished outcomes for teachers and students. The Integrated Literacy Study Groups professional development was designed to support the needs of teachers of students with or at-risk for emotional and behavioral disorders by integrating components of social-emotional learning and literacy instruction. The present study uses structural equation modeling to evaluate how and to what extent teacher beliefs, targeted in training through collaborative work groups and coaching experiences, mediate the relationship between the Integrated Literacy Study Groups and student reading achievement. Among a sample of 74 elementary school teachers, we found a directional relationship such that training influenced (1) beliefs pertaining to action, (2) beliefs pertaining to self, and (3) student reading outcomes. Beliefs pertaining to self was a significantly stronger mediator of the relationship between professional development and student reading outcomes. We discuss potential reasons for these findings as well as their implications for the design of training of teachers of students with or at-risk for emotional and behavioral disorders. [For the corresponding grantee submission, see ED624128.]