BACKGROUND: Dietary factors are among the largest and costliest drivers of chronic diseases in England. As a response, the government implements a range of population interventions to promote healthy diets by targeting food environments. OBJECTIVES: This study aimed to conduct a systematic review of the effectiveness, cost-effectiveness and policy process of real-world evaluations of national and state policies on improving food environments, with a focus on whether they were regulatory, voluntary or partnership approaches. DATA SOURCES: Fourteen relevant English-language databases were searched in November 2020 for studies published between 2010 and 2020. METHODS: Six separate evidence reviews were conducted to assess the evidence of effectiveness, cost-effectiveness and policy processes of policies to improve food environments. RESULTS: A total of 483 primary research evaluations and 14 evidence syntheses were included. The study reveals considerable geographic, methodological and other imbalances across the literature, with, for example, 81% of publications focusing only on 12 countries. The systematic reviews also reveal the effectiveness and cost-effectiveness of reviewed regulatory approaches designed to improve health, consumer behaviour and food environment outcomes while public-private partnerships and voluntary approaches to improve diets via reformulation, advertising and promotion restrictions or other changes to the environment were limited in their effectiveness and cost-effectiveness. The study also revealed key enabling and impeding factors across regulatory, voluntary and public-private partnership approaches. CONCLUSION: From the available evidence reviewed, this study finds that regulatory approaches appear most effective at improving the food environment, and voluntary agreements and partnerships have limited effectiveness. These findings should be carefully considered in future public health policy development, as should the findings of geographic imbalance in the evidence and inadequate representation of equity dimensions across the policy evaluations. We find that food policies are at times driven by factors other than the evidence and shaped by compromise and pragmatism. Food policy should be first and foremost designed and driven by the evidence of greatest effectiveness to improve food environments for healthier diets. LIMITATIONS: This was a complex evidence synthesis due to its scope and some policy evaluations may have been missed as the literature searches did not include specific policy names. The literature was limited to studies published in English from 2010 to 2020, potentially missing studies of interest. FUTURE WORK: Priorities include the need for guidance for appraising risk of bias and quality of non-clinical studies, for reporting policy characteristics in evaluations, for supporting evaluations of real-world policies equitably across geographic regions, for capturing equity dimensions in policy evaluations, and for guideline development for quality and risk of bias of policy evaluations. STUDY REGISTRATION: This study is registered as PROSPERO CRD42020170963. FUNDING: This award project was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme (NIHR award ref: NIHR128607) and is published in full in Public Health Research; Vol. 12, No. 8. See the NIHR Funding and Awards website for further award information.