Currently occurring at epidemic levels in Aotearoa New Zealand, childhood obesity warrants urgent policy intervention. Well-informed policy for complex issues is essential, however, little is known about how children have informed past Aotearoa policy about childhood obesity. This research project sought to understand this case using Merriam’s case study methodology with data from four relevant policies and six policy contributors. A qualitative analysis demonstrated that child participation in policy about childhood obesity was minimal due to low visibility or invisibility of children during policy development. Childhood obesity is complex, and children experienced cultural exclusion and restrictive advocacy from adults operating in a culture of child invisibility. A discussion of these findings culminated in a recommendation to policymakers to write future policy about childhood obesity within a new culture of child visibility. In this theoretical policy culture, child participation needs to be included to overcome problematic issues of power created by adults. However, future policy needs to be predicated on rights-based documents to enforce participation. Lastly, child participation and visibility are sustained by citing issues of social injustice as a leading cause to childhood obesity. The findings of this study around policy cultures could have implications for future Aotearoa childhood obesity policy and other child policies where health inequities are a prominent factor.