Objective: Research on the consequences of breakfast skipping among students tends to focus on academic outcomes, rather than student wellbeing or engagement at school. This study investigated the association between breakfast skipping and cognitive and emotional aspects of school engagement. Design: Cross-sectional study using data from a population level survey of children and adolescents' wellbeing and engagement at school. Linear regression with adjustment for confounders was used to estimate the effect of breakfast skipping on school engagement. Setting: Government schools (i.e. public schools) in South Australia. Participants: The participants were students, Grades 4 to 12, who completed the Wellbeing and Engagement Collection in 2019. The analysis sample included 61,825 students. Results: 9.6% of students reported always skipping breakfast, with 35.4% sometimes skipping, and 55.0% never skipping. In the adjusted linear regression models, children and adolescents who always skipped breakfast reported lower levels of cognitive engagement (β = -0.26 (95% CI -0.29, -0.25)), engagement with teachers (β = -0.17 (95% CI -0.18, -0.15)), and school climate (β = -0.17 (95% CI -0.19, -0.15)), compared to those who never skipped breakfast, after controlling for age, gender, health, sleep, sadness and worries, parental education, socioeconomic status, and geographical remoteness. Conclusion: Consistent with our hypothesis, skipping breakfast was associated with lower cognitive and emotional engagement, which could be due to mechanisms such as short-term energy supply and long term health impacts. Therefore, decreasing the prevalence of breakfast skipping could have a positive impact on school engagement.