This study uses data from the first three waves of the National Longitudinal Study of Adolescent Health, from 8,019 adolescents and their mothers, to examine links between multiple dimensions of family structure and instability over adolescents’ life courses, family functioning, peer contexts, and teenage cohabitation. Investigated explanations include an instability model, socioeconomic-stress model, and intergenerational transmission. Results from logistic regression models link single-mother and stepfamily residence during adolescence to frequent family transitions, weakened maternal bonds, teenage dating, and, ultimately, teenage cohabitation. Moreover, single motherhood and maternal cohabitation fail to predict teenage cohabitation among those living in stable households. Individual poverty and residence in a neighborhood marked by family disruption account partially for the influence of single motherhood. In addition, maternal bonds moderate the influence of maternal cohabitation on adolescent cohabitation, yielding support for an intergenerational transmission effect.