Abstract Background Health literacy (HL) is a modifiable factor contributing to the promotion and maintenance of health and well-being throughout an individual’s life. Identified as a priority in Wales, UK in 2010, progress has since stalled despite health and education as national policy priorities and international policy growth. There is a gap in understanding of children in Wales’ HL needs, particularly below adolescent age ( < =11 years). Methods This study aimed to scope a measure of children’s HL to be integrated into the existing HAPPEN Cohort Study survey, which collects self-reported health behaviours of children aged 8-11. A review identified the Health Literacy of School-Aged Children (HLSAC) tool which conceptualises health literacy as a learning outcome. A convenience sample of n = 15 primary schools were recruited in April 2023 through HAPPEN and n = 669 school children n = 669 completed the online survey between May-June 2023. Results Preliminary data using sum HLSAC scores show a proportion of children with low (20.5%), moderate (52.8%) and high HL (26.8%). Independent samples t-tests comparing mean HLSAC scores with binary self-reported health behaviours show higher HL scores for weekly behaviours (p < 0.05); feeling less tired (0-4 days: 15.1+-4.1, > =5 days 14.5+-3.4), can concentrate (0-4 days: 14.3+-3.6, > =5 days: 15.5+-4.0) and consume less fizzy drinks (0-4 days: 15.0+-3.9, > =5 days: 14.0+-3.8). Further, for can ride a bike (no: 14.3+-4.0, yes: 15.0+-3.9), can swim 25m (no: 14.6+-3.7, yes: 15.1+-4.0), someone active in the household (no: 14.3+-3.8, yes: 15.2+-4.0) and higher health well-being (<7/10: 13.9+-3.5, > =7/10: 15.3+-3.9). This preliminary data will be strengthened with further analyses including regression. Conclusions Associations appear between various important health behaviours spanning physical activity, nutrition, cognition and wellbeing. Capturing children’s HL and health behaviour needs enables targeted health promotion and education activities.