Abstract Background Health information is increasingly available and plays a crucial role in making health decisions and developing healthy behaviours. Digital health literacy (DHL) enables one to distinguish between true and false health information online. Studies have found higher health literacy to be associated with healthier behaviour. However, there is no research on child DHL and health behaviour. This study aims to investigate the relationship between DHL and selected health behaviour of schoolchildren in Germany. Methods This cross-sectional study is based on a representative sample of (N = 1448) secondary schoolchildren (aged 9-18 years) in Germany across all 16 federal states and school forms. DHL was assessed using the child and adolescent version of the Digital Health Literacy Instrument developed and pretested in this study. Selected health behaviours (eating, teeth brushing, smoking, and alcohol consumption) were measured using self-report scales. Chi-square tests were conducted to measure differences between DHL and health behaviour. Results Associations were found between DHL and all eating behaviours (fruits; vegetables and salad; whole-grain products; other animal-based products; chocolate or other sweets; sugary drinks; fast food), except for eating meat and sausages. Schoolchildren with higher levels of DHL reported more often about regular consumption of fruits and vegetables (X2 (2)=17.06, p = <.001). salads (X2 (2)=56.54 p = <.001) and whole-grain-products (X2 (2)=98.81 p = <.001). While DHL was associated with teeth brushing (X2 (2)=44.46, p = <.001), no differences were observed for smoking (X2 (2)=1.93, p=.381) and drinking alcohol within the last 30 days (X2 (2)=2.62, p=.270). Conclusions These findings indicate that most health behaviours of schoolchildren may benefit from enhancing DHL in schools. Programs should build around these topics. However, more research is needed to investigate associations between DHL and health behaviours comprehensively.