Improved understanding of how to advance national nutrition policy is critical to ensure greater policy investments in nutrition. We used a participant-observer, change-agent model to prospectively study why and how national nutrition policy advanced in Vietnam between 2006 and 2008. Our goal was to understand strategies used, factors that shaped policy advancement, and the interaction of strategies with factors in this context. Data were collected using questionnaires, informant interviews, programme visits, document reviews and documentation of key events. For analysis, we created a chronology of events, examined strategies and actions used and their results by event, coded interviews and summarized findings using a well-known framework for policy analysis. Our analysis shows that the following elements were critical to bring greater attention to nutrition policy in this context: (1) building a cohesive nutrition policy community through creation and support of an alliance; (2) clearly defining internal and external frames for the nutrition problem; (3) using and creating high-profile internal and external policy windows; and (4) capitalizing on cultural motivations and values. Findings indicate that that rapid nutrition policy advancement is possible if purposeful, contextually sensitive strategies are used where favourable conditions exist, or can be created. The participant-observer, change-agent model was successful in both contributing to policy advancement and documenting it.