The purposes of this study were to examine the relationships among mental health status, demographic characteristics, and social contexts, including family conflict and support, connectedness to school, and affiliation with peers who exhibit delinquent behavior and who use substances, among Taiwanese aboriginal adolescents. A total of 251 aboriginal junior high school students in an isolated mountainous area of southern Taiwan were recruited, and the relationships among mental health status, demographic characteristics, and social contexts among them were examined using a structural equation model (SEM). The SEM revealed that family conflict and support had direct influences on mental health status and connectedness to school. Family conflict had a direct relationship with affiliation with peers who use substances, and family conflict and support were both indirectly linked with affiliation with peers who exhibit delinquent behavior and who used substances; these were mediated by a poor mental health status. Female and older age were directly linked with a poor mental health status and were indirectly linked with a greater number of peers who exhibit delinquent behavior and who use substances via the poor mental health status. Disruptive parenting was directly linked with affiliation with peers who use substances. The authors suggest that those who devise strategies to improve aboriginal adolescents' mental health and discourage substance use should take these relationships among mental health, demographic characteristics, and social contexts into account.