School meals can be an essential part of child health and nutrition; they are central to school-aged children’s food environments and often fulfil a substantial portion of a child’s daily nutritional requirements. In Vietnam, ensuring nutritional school meals has been prioritised through resolutions, projects, national strategies, guidelines, circulars, and do- cuments concerning school meals, all aimed at promoting good nutrition and preventing diet-related disorders in children. Challenges to implementing such policies persist, par- ticularly in urban areas. We employ decision analysis (DA) to evaluate current policies’ effectiveness and identify potential implementation risks, including external risks. We inte- grated literature, observational data, and stakeholder consultations to assess the impacts of ongoing school meal policies and the impact of these on children’s nutrition. We as- sess existing school nutrition policies in Vietnam to assess their effectiveness in enhancing children’s nutritional intake and identify potential risks to implementation. We generated a graphical impact pathway to express the case for the schools, including all costs, benefits and related risks of the existing investments. We follow up using Monte Carlo simulations to forecast nutrition outcomes and the cost reduction for health care. We further calculated the value of information for every input variable. Preliminary model results indicate how the internal (i.e. risks of implementation within the school and education systems) and external risks (e.g. school gate food, which is beyond the school’s control) can potentially disrupt the intended impact of policies and, ultimately, child nutrition. Our model provides valuable insights for monitoring and adapting school meal policies in urban Vietnam. By emphasising evidence-driven policymaking, we showcase a method for addressing nutritio- nal challenges in children’s food environments through a rigorous and holistic analysis of potential policy interventions. We see enormous potential for evidence-driven and adaptive policymaking as a crucial tool in addressing the complex and multifaceted challenges of interventions to food environments and impacts on children’s health.