Teachers' social self-efficacy is an important construct that has not been examined adequately in education yet. Developing a comprehensive understanding of teachers' social self-efficacy requires measuring these beliefs in the social domain of teachers' functioning. This study developed the Teachers' Social Self-Efficacy Scale (TSSES) scale and investigated its psychometric properties in a total sample of 650 preschool teachers from Greece. Results from factor analysis revealed a bi-factor model underlying a global TSSE factor and five specific factors. Evidence of validity was obtained with the TSSES prediction on the closeness and conflict dimensions of teacher--student relationship quality. Findings showed that the TSSES can be considered as a valid and reliable instrument. Implications and directions for further research are discussed.