Purpose: A school nutrition policy (SNP) is one promising school-based health promotion strategy to improve the food environments of First Nations children. The aim of this study was to explore First Nations parents' perceptions of a SNP. Methods: A process evaluation of policy implementation was conducted using a mixed-methods design. Parents (n = 83) completed a 19-question survey to capture their perceptions of the policy. Survey responses informed questions in an 11-question semi-structured interview guide. Transcripts from interviews with parents (n = 10) were analyzed using content analysis to identify barriers and facilitators to policy implementation. Results: Parents were supportive of the SNP and the school's food programs, which they perceived as helping to address community concerns related to nutrition. However, some parents opposed the restriction of unhealthy foods at school celebrations and fundraisers. In addition, despite being aware of the SNP, parents were unable to demonstrate an understanding of the SNP content. Finally, parents struggled to provide their children with healthy foods to bring to school due to lack of affordable and accessible food in the community. Conclusions: Although SNPs may be well-received in First Nations communities, their implementation must be supported by parent involvement and consideration of wider socioeconomic conditions.