Objective: To examine potential mediating and moderating factors in the longitudinal association between contextual stressors (economic hardship, ethnic discrimination) and subsequent engagement in risky behaviors and body mass index (BMI) of Mexican-origin adolescent mothers. Method: Participants were Mexican-origin adolescent mothers (N = 204) who were recruited from community agencies and high schools in a Southwestern metropolitan area. Contextual stressors and risky behaviors were assessed 3 and 4 years postpartum. Adolescent mothers’ BMI was assessed 5-years postpartum. Path analyses assessed moderated mediation with risky behaviors as a mediator of associations between contextual stressors and BMI, and family and friend support as moderators of the mediated pathways. Results: At low levels of family support, economic hardship at 3-years postpartum positively predicted engagement in risky behaviors at 4-years postpartum, which in turn positively predicted BMI at 5-years postpartum. At high levels of family support, all relations were not significant. At low levels of friend support, ethnic discrimination at 3-years postpartum positively predicted engagement in risky behaviors at 4-years postpartum, which in turn positively predicted BMI at 5-years postpartum. At high levels of friend support, all relations were not significant. Conclusions: Among adolescent mothers who receive low levels of family and friend support, engagement in risky behaviors may function as a mechanism through which contextual stressors are linked to adolescent mothers’ BMI. Findings have implications for prevention efforts aimed at attenuating unhealthy weight status among Mexican-origin adolescent mothers by reducing engagement in risky behaviors and bolstering family and friend support.