Increasing numbers of overweight and obese youth draw attention to the school as an important setting for targeted nutrition interventions, given that it is where they spend a majority of their waking time. The objective of the present study was to explore local-level factors shaping the implementation of a school nutrition policy. In-depth, semi-structured interviews were conducted in person or via the telephone (a maximum of 60 min). An interview guide was informed by the Analysis Grid for Environments Linked to Obesity (ANGELO) framework, research objectives and literature. Key themes centred on policy implementation, including facilitators and barriers (i.e. resources, capacity), user satisfaction (i.e. students) and communication strategies. Setting: Secondary schools in Ontario, Canada. Subjects: Twenty-two participants from local agencies supporting school nutrition programming (n 8) and secondary-school principals, vice principals and teachers (n 14) from nine schools across three Ontario school boards. Results: Results are organized according to environments outlined in the ANGELO framework. The cost of healthy food for sale, revenue loss (economic), proximity of schools to off-site food outlets (physical), the restrictive nature of policy, the role of key stakeholders (political), the role of stigma and school culture (sociocultural) act as local-level barriers to policy implementation. Conclusions: Gaps in policy implementation include the high cost of food for sale and subsequent revenue generation, the close proximity of internal and external food environments, the need for consultation and communication between stakeholders, and strategies to reduce stigma and improve the school nutrition culture.