Abstract Today’s society exposes children to vast amounts of health-related information, presenting significant challenges in navigating this content. European health literacy (HL) research underscores the primary school’s role in educating children’s HL. Several HL interventions have been developed for a school setting and few have used co-design with adolescents. However less is known about co-designing HL activities with children. Therefore, this study aims to identify barriers and facilitators for co-designing HL activities with 9 to 12-year-old children in school settings. We use 4 phases of design-based research for the process of co-designing learning activities with multiple teams of 6-8 children in school settings. First, children Reflect on HL and empathize and define skills they want to design activities for. They Design activities through ideation and prototyping. We use a variety of creative methods for the sessions and analyses, such as body mapping and affinity mapping. The evaluation of the effectiveness regarding HL and learning outcomes will be performed in Test and Evaluate phases. Our preliminary results show that children need short and clear assignments for the sessions to reach the goals. Children are enthusiastic to participate and like the methods used in the session, although the concept of HL is sometimes difficult to comprehend. It is challenging for children to come up with creative and appropriate elements for activities without correct health information. We are awaiting results from Test and Evaluate phase on the effect on HL levels and learning outcomes. Children are able to co-design HL activities together with HL and health promotion researchers. By giving children a voice and hands-on experience in the design process, we are able to create activities that are suitable for the target population. This co-design process will be evaluated and adapted to an intervention for the “healthy school” program in the Netherlands. Key messages • By co-designing HL activities children actively learn about health literacy. • Children are important and capable co-designers for HL activities when working together with HL researchers.