This article presents data from the 2014 HBSC survey on the social support perceived by middle school students, according to their sociodemographic profile. It explores the relationships between perceived social support and certain indicators or determinants of adolescent health (mental health, violence, and substance use). Seven out of ten middle school students perceive a high level of support from their families and an equal number from their peers. These two dimensions of social support are unevenly distributed according to gender, family structure, or economic status and evolve differently between sixth and ninth grade. A comparison of the two sources of social support shows a clear predominance of perceived family support on mental health, violence, and experimentation with psychoactive substances during adolescence. [author’s abstract]