BACKGROUND: Circadian disruption has been proposed as an etiological mechanism for psychopathology, yet its role in the relationship between screen use and emotional and behavioral problems remains under-investigated. This study aimed to examine the mediating effect of circadian rhythm in this relationship among young children. METHODS: This cross-sectional study analyzed data from 1111 children aged 2 to 7 years recruited from six kindergartens between March 2022 and June 2024. Parents reported children's screen time and use before sleep. Parents and teachers assessed internalizing and externalizing problems using the Strengths and Difficulties Questionnaire. Circadian rhythm, including chronotype and midsleep on free days corrected for sleep debt (MSF RESULTS: Screen use was significantly associated with parent-reported internalizing and externalizing problems. Chronotype significantly mediated the relationships between screen use and parent-reported outcomes, whereas the results were not reproducible using MSF CONCLUSION: The mediation of delayed circadian phase in the relationship between screen use and internalizing and externalizing problems in young children may be negligible. Future research should explore the role of other circadian parameters in this relationship. IMPACT STATEMENT: Circadian disruption has been suggested as a potential mechanism linking screen-based media exposure to psychopathology. Using a triangulation approach that combined multiple data sources-survey, actigraphy, and sleep diaries-we found that the mediating effects of delayed circadian phase in the relationships between screen use and internalizing and externalizing problems were minimal in children aged 2 to 7 years. Future research should explore alternative circadian pathways and examine the long-term developmental effects of screen use during early childhood.