This study addresses preschool teachers' self-efficacy beliefs in assessment and promotion of children's early language, social-emotional, and mathematical skills. The aim of the study was to find out to what extent preschool teachers believe to be able to assess and promote those skills, respectively. In a sample of 368 German preschool teachers, average scores in all scales were quite homogenously high. However, average scores of self-efficacy beliefs between the domains differed, with self-efficacy beliefs regarding language skills being the strongest. Self-efficacy beliefs regarding assessment were stronger than in promotion in the social-emotional and the mathematical domain, but not in language. Yet, confirmatory factor analyses indicate that self-efficacy beliefs regarding assessment were highly correlated with self-efficacy beliefs regarding promotion of skills in all three domains. Possible explanations for these results and ideas for further research are discussed.