Background Despite global recommendations to prioritise policies that create healthy food environments within education institutions, the implementation of effective healthy school food policies has proved challenging for many countries. This study examined the experience of Samoa subsequent to the 2012 introduction of a stronger policy to improve the healthiness of school food environments. Our aim was to identify opportunities to strengthen healthy school food policy implementation in Samoa and other comparable contexts. Methods We used a qualitative case study approach, underpinned by policy science theory. In 2018, we conducted in-depth semi-structured interviews with 30 informants, coupled with analysis of relevant documents, to generate a detailed understanding of the relevant policy implementation processes in Samoa, and the perspectives and capacities of key implementation actors. Data collection and analysis were guided by the Health Policy Analysis Triangle, supplemented by other policy theories relevant to policy process. Results Samoa’s school food policy operationalizes international ‘best practice’ recommendations. We found health policymakers and leaders in Samoa to be strongly committed to improving school food environments. Despite this, there continued to be challenges in ensuring compliance with the school nutrition standards. Key issues that negatively impacted the policy’s effectiveness were the lack of priority given to school food by stakeholders outside of health, the high prevalence of unhealthy food in the areas immediately surrounding schools, vendor knowledge and capacity, and the high degree of agency exercised by actors in and around the school. We noted several opportunities for policies to be effectively implemented and sustained. Respondents identified community-level leaders as potentially pivotal stakeholders, particularly where school governance arrangements draw heavily on community representation. Conclusions Sustained and effective implementation of healthy school food policies requires continued engagement from political and community leaders, beyond initial commitment. There is potential to capitalize on political will for diet-related NCD prevention by more clearly demonstrating the institutional and operational requirements for effective and sustained implementation. Strong incentives for compliance and effective enforcement mechanisms are also likely to be crucial to success.