Regular science practices in preschool are crucial for children's learning in science. Yet, preschool teachers may only offer science learning opportunities if they "are" and "feel" sufficiently qualified to teach early science. The present study investigates the relation between teachers' qualifications, their self-efficacy beliefs in science and the frequency of teachers' science practices based on 348 German preschool teachers. Regression results showed that teachers' practices were associated with their science-specific educational training and their participation in professional development in science, but not with their general educational degree. Furthermore, results from structural equation modelling revealed that the relation between professional development and teachers' science practices was mediated by their self-efficacy beliefs in science. These results underline the relevance of teachers' science-specific qualifications as well as teachers' self-efficacy beliefs for their science practices.