Childhood obesity is an increasing health problem. Prior empirical research suggests that, although discussing lifestyle behaviours with parents could help prevent childhood obesity and its health-related consequences, physicians are reluctant to address parental responsibility in the clinical setting. Therefore, this paper questions whether parents might be (or might be held) responsible for their children’s obesity, and if so, whether parental responsibility ought to be addressed in the physician–patient/parent encounter. We illustrate how different ideal-typical models of the physician–patient/parent interaction emphasise different understandings of patient autonomy and parental responsibility and argue that these models advocate different responses to an appeal for discussing parents’ role in childhood obesity. We suggest that responsibility should be attributed to parents because of their parental roles in providing for their children’s welfare. We also argue that whether, and how, this responsibility gives rise to a requirement to act depends on the parents’ capacities. A deliberative-oriented physician–patient/parent interaction best captures the current ideals of antipaternalism, patient autonomy, and shared and evidence-informed decision-making, and might facilitate parental role development. We conclude that, while not discussing parental responsibility for childhood obesity in the clinical setting can be warranted in particular cases, this cannot be justified as a general rule.