Unhealthy food marketing shapes children’s preference towards obesogenic foods. In Malaysia, policies regulating this food marketing were rated as poor compared to global standards, justifying the need to explore barriers and facilitators during policy development and implementation processes. The case study incorporated qualitative methods, including historical mapping, semi-structured interviews with key informants and a search of cited documents. Nine participants were interviewed, representing the Federal government (n = 5), food industry (n = 2) and civil society (n = 2). Even though the mandatory approach to government-led regulation of food marketing to children was the benchmark, more barriers than facilitators in the policy process led to industry self-regulations in Malaysia. Cited barriers were the lack of political will, industry resistance, complexity of legislation, technical challenges, and lack of resources, particularly professional skills. The adoption of industry self-regulation created further barriers to subsequent policy advancement. These included implementer indifference (industry), lack of monitoring, poor stakeholder relations, and policy characteristics linked to weak criteria and voluntary uptake. These underlying barriers, together with a lack of sustained public health advocacy, exacerbated policy inertia. Key recommendations include strengthening pro-public health stakeholder partnerships, applying sustained efforts in policy advocacy to overcome policy inertia, and conducting monitoring for policy compliance and accountability. These form the key lessons for advocating policy reforms.