The aim of the study is to comprehensively analyze the interrelationships between teacher efficacy, the sources of self-efficacy, and implementation of early childhood education (ECE). The assumption is that according to socio-cognitive theory, source categories predict the self-efficacy of educational staff. According to a few previous research results, knowledge of theories and research in the field of education also contributes to a professional's self-efficacy. In this study, 202 Finnish ECE teachers evaluated their self-efficacy and its sources (mastery experiences, vicarious experiences, social persuasion, and physiological arousal) as well as their pedagogical planning, implementation, and leadership. A path analysis was conducted to estimate the sources of self-efficacy and active and reactive use of educational research as predictors of teacher self-efficacy, and further, of self-efficacy as a predictor of teachers' pedagogical planning, implementation, and leadership. The findings showed that mastery experiences, social persuasion, and physiological arousal were positively related to self-efficacy in pedagogical approaches, group management, and child engagement. Intentional use of educational theory and research was positively related to self-efficacy in pedagogical approaches. Furthermore, the quality of pedagogical planning, implementation, and leadership were predicted by high self-efficacy in pedagogical approaches, but implementation also by social persuasion and active use of theory and research.