Objective: To understand the relationship between adolescents' unhealthy snacking behaviour during their school journey and their perceived and objective measures of food outlet availability in the school neighbourhood.

Design: A cross-sectional survey enquired about socio-demographic information, school transport modes, perceived presence of food outlets in the school neighbourhood and unhealthy food purchase and consumption on the school journey. A geographical information system analysis of the food outlets within 500 m and 1000 m school buffers was undertaken. Data were analysed using generalised linear mixed modelling.

Setting: All twelve secondary schools in Dunedin, Aotearoa New Zealand, March 2020-June 2022. Participants: Adolescents aged 13-18 years (n 725) who reported being familiar with their school neighbourhood.

Results: Perceived availability of food outlets in the school neighbourhood was inversely correlated with distance to the closest food outlet from school and positively correlated with food outlet density within 500 m and 1000 m school buffers. Adolescents' purchase and consumption of unhealthy snacks and drinks during the school journey were associated with perceived availability of food outlets and with shorter distance to the closest food outlet from school. Mixed transport users, girls and those living in high-deprivation neighbourhoods had higher odds of purchasing and consuming unhealthy snacks and drinks during the school journey than active transport users, boys and those living in low-deprivation neighbourhoods, respectively.

Conclusions: Adolescents perceptions of the food environment and close access to food outlets in the school neighbourhood may influence adolescents' food purchase and consumption behaviours during the school journey.