Food environments can play important roles in shaping nutrition and health outcomes. One such environment that has potential to affect youth is the school food environment. In contrast to higher-income countries, however, there is a critical evidence gap on the role of school food environments on children and adolescents in low- and middle-income countries. This mixed-methods study contributes to filling this gap by investigating the role of school food environments on dietary behaviours of children and adolescents in Ghana. It draws on data from household and school questionnaires as well as focus group discussions collected as part of the baseline for an impact evaluation of the Ghana School Feeding Programme (GSFP). Multi-level regression models were fitted with random intercepts at the individual, household and community levels. Excerpts from the focus group discussions provided a deeper understanding of quantitative findings. Children and adolescents who received free school meals provided by the GSFP or who lived further away from school were less likely to go home for lunch. More than half of sampled schools reported offering foods for sale by independent vendors, the most common being meals followed by confectionery, fruit and sugar-sweetened beverages. Predictors of bringing money to school to buy food included non-receipt of free school meals, adolescence, greater commuting distance from home, household asset score, and urban location. Policy efforts focusing on the school food environment may contribute to healthy dietary behaviours for children and adolescents with positive impacts over the lifecourse.