Aims: Studies have shown that gambling is associated with poor health and health risk-taking behaviour. However, little is known about those factors that can influence the association between gambling, health risk-taking and health. Using a population-based School Health Promotion Study of eighth- and ninth-grade Finnish boys and girls (N = 62,956), we investigated the relationships between gambling frequency, health risk-taking and poor health as well as whether social support from parents, friends and school staff could mediate these associations. Methods: Path analysis was used to discover direct and indirect effects of health, health risk-taking and gambling. Results: Social support from parents and school staff decreased gambling among boys and girls, whereas among boys support from friends increased gambling. However, the role of social support as a mediator was very weak. Overall poor health and health risk-taking were associated with increased gambling. Conclusions: Gambling should be considered an important public health issue because it clusters with other unhealthy behaviour patterns. Interventions concerning adolescent gambling should also take other simultaneous risk-taking into consideration. Also social support from parents and school should be noted when trying to decrease adolescents’ gambling.