Obesity among adolescents is a significant public health issue, with increasing prevalence globally. The school food environment plays an important role in shaping adolescent students’ food choices, but there is a notable research gap exploring adolescents’ perceptions of their school food environment. This study explored how the external school food environment was perceived by secondary students and how it influenced their food behaviours. Four focus groups were conducted in June 2024 with 31 students from a secondary school in Perth, Western Australia. The school was purposively selected as it was located opposite a retail food precinct comprising ten external food outlets. Facilitators used semi-structured questions to guide the focus group discussions. The food outlets’ extended opening hours and close proximity to the school increased students’ purchase and consumption of unhealthy food. Students’ preference for unhealthy food and drinks was influenced by their relative affordability compared to healthier items. The external food outlets provided a meeting place for students to socialise, often resulting in anti-social behaviour (e.g. stealing, loitering and vandalism). Students observed unhealthy food outlet advertising on their school commute and from within the school. Recommendations to improve the external school food environment included initiating planning laws to restrict the presence of fast-food outlets near schools and increasing the cost of unhealthy food. This research provides insights into how the accessibility of the external food environment, availability and affordability of unhealthy food, exposure to advertising and social appeal of food outlets influence adolescents’ food preferences and behaviours. strategies to improve their external school food environment, including government interventions that address the accessibility and marketing of unhealthy food near schools.