Health policies aim to achieve specific health goals through system-level changes, unlike common health interventions that focus on promoting specific health behaviors on individual level. However, reliable data on the feasibility and implementation of policy actions across Europe are lacking. Moreover, no practice-oriented guidance exists for policy makers and implementers on how to evaluate policy implementation.As part of the Policy Evaluation Network, we aimed to synthesise knowledge on how to evaluate the implementation of policies promoting healthy diets, physical activity, and reducing sedentary behaviours. The multidisciplinary working group comprised 16 researchers and conducted two scoping reviews, three systematic reviews, two meta-reviews, two qualitative case studies and one quantitative case study over three years. The target populations included the general population, those at risk for obesity, and school children. Based on these reviews and case studies, this article summarises and presents the findings and lessons learned regarding the implementation evaluation of policies in nine case reports.Drawing on these experiences, three critical requirements for policy implementation evaluation were set: 1) conduct a comprehensive policy implementation evaluation from a multi-level perspective, 2) use implementation frameworks to address processes, determinants, and outcomes, and 3) engage relevant stakeholders in policy implementation evaluation. Finally, the consensus process resulted in 10 steps for the implementation evaluation of policies to promote physical activity and a healthy diet and to reduce sedentary behaviours, which adhere to the requirements and resources of the targeted policy.The findings of an implementation evaluation can lead to a better understanding of why policies work or not and can serve as a basis for developing solutions. This practice-oriented guidance outlines factors that should be considered in policy implementation evaluation to address its complexity. In this way, involved researchers and practitioners are empowered to engage in the evaluation process to close the knowledge gap regarding policy implementation.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12889-023-15775-9.