Pedagogical competence and teaching efficacy significantly influence the quality of classroom science learning. Without applying pedagogical learning in realistic classroom environments, there is slight possibility that prospective teachers will increase their teaching confidence or develop understanding of how learners acquire and construct knowledge. The current shift in science education reform calls for students to experience how science is authentically enacted. Twenty-two undergraduate teacher candidates were placed at an elementary school for teacher preparation studies and for opportunities to apply their coursework learning. This quantitative study sought to determine if teacher candidates' self-efficacy increased due to participation in a field-based elementary science methods course with integrated teaching practice consisting of mentoring fifth grade students in investigative science projects. Pretest and posttest STEBI-B data indicate that general (d = 0.93) and personal (d = 0.90) science teaching efficacy increased significantly. The increase in outcome expectancy was not significant (d = 0.38).