This study examined early development of cool and hot self-regulation and how they were related to Chinese preschoolers' early achievement. A total of 951 children (448 girls) aged three to five in Hong Kong participated in this study. Children's self-regulation was assessed with a battery of five tasks tapping either cool or hot self-regulation; early child development was assessed with items selected from the Hong Kong Early Child Development Scales. Mothers reported children's behaviors according to items selected from the Strengths and Difficulties Questionnaire to understand children's emotional and behavior problems. The results identified a complex relationship between cool and hot self-regulation and cool and hot self-regulation were also found to predict children's achievement differently. These findings suggest the unique role of cool and hot self-regulation in early years and the importance of integrating both the cool and hot aspects of self-regulation in the research and practice arenas. Copyright © 2020 Informa UK Limited, trading as Taylor & Francis Group.