Background: Although school nutrition policies (SNPs) have been highlighted as an important intervention to support childhood nutrition, their implementation and maintenance within real-word settings is complex. There is a need to understand the factors that influence implementation by consolidating existing research and identifying commonalities and differences. Aims: The purpose of this review is to determine what is known about the influence of broad and local system factors on the implementation of SNPs internationally. Method: This scoping review involved identifying and selecting relevant literature that related SNP implementation in primary and secondary schools. Following the search process, 2,368 articles were screened and 59 articles were synthesized and charted and emerging themes were identified. Results: Across the final studies identified, factors emerged as barriers and facilitators to the implementation of SNPs, with system implications that related to five areas to support policy action: providing macro-level support may encourage policy implementation; addressing the financial implications of healthy food access; aligning nutrition and core school priorities; developing a common purpose and responsibility among stakeholders; recognition of school and community characteristics. Discussion: While SNPs can help to support childhood nutrition, strategies to address issues related to policy implementation need to be taken to help schools overcome persistent challenges. Conclusion: The results of this review provide opportunities for action across multiple system levels to ensure synergy and coordinated action toward SNP goals to foster the creation supportive nutrition environments for children.