Bandura (1997) contends that when compared to other sources of efficacy, mastery experiences, when presented appropriately, have the most powerful influence on self-efficacy. The purpose of this study was to investigate the effects of community-based service learning (CBSL) experiences on preservice elementary teachers' personal self-efficacy beliefs about equitable science teaching and learning. Data were collected using pretests-posttests and post-questionnaires with the study sample. Findings from this study support Bandura's assertion. CBSL experiences were an important source of personal self-efficacy and significantly influenced preservice elementary teachers' personal self-efficacy beliefs about equitable science teaching and learning.