Background: During the adolescent period, risktaking behaviour increases. These behaviours can compromise the successful transition from adolescence to adulthood. The purpose of this study was to examine social support as a mediator of the relation between problem behaviour and gambling frequency among Finnish adolescents. Methods: Data were obtained from the national School Health Promotion Study (SHPS) from the years 2010 and 2011 (N=102 545). Adolescents were classified in the most homogeneous groups based on their problem behaviour via latent class analysis.Results: Path analysis indicated that social support was negatively associated with problem behaviour, and problem behaviour and social support were negatively related (except for social support from friends among boys) to gambling. Social support from parents and school mediated, albeit weakly, the relations between problem behaviour and gambling among girls and boys. Conclusions: Problem behaviour may affect gambling through social support from school and parents. Thus prevention and intervention strategies should focus on strengthening adolescents’ social support. In addition,because of the clustering of different problem behaviours instead of concentrating on a single form of problem behaviour multiple-behaviour interventions may have a much greater impact on public health.