Science is an important domain in early childhood education. Though, initial results indicate that preschool teachers rarely offer science activities. Against this background professional development aims to encourage preschool teachers to provide science activities more frequently. In Germany, professional development is often offered as short-term courses. It is not clear whether the participation in these courses results in an increase of the frequency of science activities and which role the work environment plays for the frequency of science activities provided by preschool teachers. Therefore the present study investigated how a supportive work environment, assessed by the indicator professional exchange on early science education between preschool teachers, is related to their amount of professional development and the frequency of their science activities for preschool children. A questionnaire was completed by 301 preschool teachers. The results revealed a positive relation between the amount of professional development in science and the frequency of science activities. Further findings indicate that this relation is mediated by the frequency of professional exchange about science content. In addition, we found that preschool teachers without any professional development provided science activities more frequently, when science content was discussed in team meetings. Implications for practice are discussed.