This study examined the implementation of critical features associated with positive behavioral interventions and supports (PBIS) in early childhood classrooms in the United States and South Korea. Each country has a distinct approach to providing early education for young children. There is some evidence that preschool teachers' approaches to managing young children's challenging behavior are influenced by cultural and contextual factors unique to each country. Differences in implementation status were measured using the Preschool-wide Evaluation Tool (PreSET) in early childhood classrooms in both countries. Preschool teachers in the United States used significantly more features of universal tier and program-wide PBIS related to defining and teaching behavioral expectations, responding to appropriate and challenging behavior, providing an organized and predictable environment, and having a leadership team and program support. South Korean teachers collaborated with families significantly more than teachers in the United States. Factors related to cultural variance in PBIS implementation are discussed. (author abstract)