Children from disadvantaged areas are hard to reach for interventions aimed at promoting healthy lifestyles. We conducted a participatory needs assessment, in which researchers collaborated with a community in a disadvantaged area in Amsterdam to gain an understanding of the health-related issues of children within this community. Qualitative data was collected through: three to four participatory group meetings with three groups of 9–12-year-old children (n = 5–9 per group); nine interviews with professionals working with youth; two interviews with parents and their children; and informal meetings including 31 parents. All transcriptions or summaries were coded and analyzed. Childhood overweight/obesity was indicated as the main health issue. A lack of physical activity and unhealthy dietary behavior were identified as the main risk factors, with underlying determinants such as culture, habits, finances, and social norms. Identified needs included more supervised, low-priced sports activities at a nearby location and more education on adopting a healthy diet. Our participatory health needs assessment resulted in a comprehensive overview of the most relevant risk factors and determinants of childhood overweight/obesity and needs from the community’s perspective. This knowledge aids in the development of better tailored, and thereby potentially more effective, interventions.