Lack of access remains a crucial barrier to improved health outcomes for children with obesity in New Zealand, according to an interview-based study. A total of 64 semi-structured interviews were conducted for 71 participants of a family-based multidisciplinary healthy lifestyle programme for children and adolescents. Half the interviews were with Māori families. Five health system factors affecting engagement were identified via thematic analysis: the national policy environment, funding constraints, lack of coordination between services, difficulty navigating the health system, and the cost of primary health care. The authors concluded that comprehensive approaches, accompanied by a clear implementation strategy and coordinated across sectors, are needed to improve engagement.