Healthier lifestyles may contribute to prevent overweight in adolescents. Although school-based interventions show promising results, adoption and implementation by secondary schools and involvement of parents is difficult. Our study aims to gain a better understanding of the problem awareness and beliefs of school staff and parents regarding adolescents' overweight and energy balance-related behaviour, their motivation for health-promoting activities and suggested actions in the school environment. Focus group interviews were conducted with three groups of parents and three groups of school staff at three pre-vocational schools in the Netherlands. Comments concerning awareness, motivation to intervene and possible actions were analysed with the Atlas.ti program. Results showed that school staff and parents were aware of overweight as a health problem, but underestimated the prevalence and impact of overweight and unhealthy behaviour in their school. Health-related behaviour of adolescents was considered primarily the responsibility of parents, but the school staff also had a pedagogical responsibility. Parents and school staff agreed that health promotion efforts would have more impact on adolescents' behaviour, when school-based activities were supported by parents and parental efforts were supported by school health promotion. Therefore, parental efforts and school-based activities should be aligned by developing and expressing shared norms about healthy behaviour and parents should be taught how to discuss healthy dietary and physical activity behaviour with their children. To tackle peer group culture and the obese environment, parents' and school staff's efforts should be part of an integrated community approach.