The purpose of this study is to provide an overview of trends in the field of early childhood education and care and examine the kind of research done outside of Japan on the concept of pedagogical content knowledge (PCK), an idea proposed by Lee S. Shulman. The study examines the applicability of PCK to the study of early childhood teachers based on a search of the Education Resources Information Center (ERIC) database. The keywords “early childhood education and care,” “PCK,” and “Shulman” were used in the database search, and ten articles that were returned were reviewed carefully. We determined that most of the studies were centered on content knowledge about mathematics, science, and technology, while only few studies focused on children’s knowledge regarding development of social skills. Some studies also focused on implicit knowledge based on Polanyi’s theory. This suggests that the PCK concept can be applied to the study of early childhood teachers in Japan as well.