e22025 Background: The lives of childhood cancer survivors (CCS) may be impacted by symptoms of neurocognitive dysfunction. Decline in executive function, one component of the construct concept of neurocognitive function, may affect the ability to be independent in later life; thus,ssessment and intervention are important. In the United States, the Childhood Cancer Survivor Study-Neurocognitive Questionnaire (CCSS-NCQ) developed by St. Jude Children’s Research Hospital has been widely utilized in clinical practice. It is a self-administered scale for screening daily difficulties regarding organization, emotional regulation, memory, and task efficiency which all fall under the concept of the executive function. To expand the tools for executive function assessment in Japan, we developed the CCSS-NCQ Japanese version and performed a validation study among the adolescent and young adult (AYA)-CCS population. Methods: The Japanese version of the CCSS-NCQ was developed by conducting linguistic validation. Japanese AYA-CCS of all cancer types were recruited and asked to complete this 32-question self-administered questionnaire. Exploratory and confirmatory factor analysis (FA) with the Promax rotation were conducted. Results: In total, 106 participants responded. The mean age of participants was 20.6 ± 5.3 years, and 49.1% were male. The mean age at diagnosis was 8.7 ± 4.8 years; 46.2% of participants were diagnosed with brain tumors, 37.7% with hematological malignancy, and 12.3% with solid tumors. The FA identified the similar four-factor structure of organization, emotional regulation, memory, and task efficiency as the original CCSS-NCQ with factor loading set at 0.4. The Cronbach’s alpha was 0.84 - 0.92. Conclusions: Neurocognitive dysfunction could be a crucial late complication of childhood cancer, and maintaining executive function, in particular, is essential for sustaining the quality of life among CCS. The CCSS-NCQ Japanese version is the first internationally translated CCSS-NCQ. The successful validation in the Japanese population will expand opportunities for future international collaboration to identify race/ethnicity-based disparities, as well as scale enhancement for application to CCS worldwide.