The purpose of this study was to investigate the impact of a mixed-reality teaching environment, called TeachME™ Lab (TML), on early childhood education majors' science teaching self-efficacy beliefs. Sixty-two preservice early childhood teachers participated in the study. Analysis of the quantitative (STEBI-b) and qualitative (journal entries) data revealed that personal science teaching efficacy and science teaching outcome expectancy beliefs increased significantly after one semester of participation in TML. Three key factors impacted preservice teachers' (PST) self-efficacy beliefs in the context of participation in TML: PSTs' perceptions of their science content knowledge, their familiarity with TML technology and avatars, and being observed by peers. Cognitive pedagogical mastery (TML practices), effective/actual modeling, cognitive self-modeling, and emotional arousal were the primary sources that increased the PSTs' perceived self-efficacy beliefs. Overall, the results of this study suggest that the TML is a worthwhile technology for learning to teach in teacher education. It provides a way for PSTs to have a highly personalized learning experience that enables them to improve their understanding and confidence related to teaching science, so that ideally someday they may translate such an experience into their classroom practices.