The purpose of this study was to investigate the effectiveness of an integrated science and mathematics methods course on preservice early childhood teachers’ efficacy beliefs for integrating science and mathematics in early childhood classrooms. Participants in two cohorts were tested to assess their efficacy beliefs for teaching science, mathematics, and integrating science and mathematics before and immediately after instruction. The findings provided evidence that the methods course was effective at enhancing preservice teachers’ efficacy beliefs for integrating science and mathematics.