Depression is known to mediate the association between low social support and parenting competence in adult mothers, but this relationship is rarely assessed in adolescent mothers and fathers. The primary aim of this study was to identify the association between social support, family functioning and social capital on parenting competence, including self-efficacy and satisfaction in adolescent mothers and their partners. Secondary aims included identifying potential partner effects (e.g. whether a partner's social support influenced the respondent's parenting efficacy). Data was obtained from a subset of participants from a longitudinal study of pregnant adolescent females and their partners. Couples completed individual structured interviews via audio computer-assisted self-interview during pregnancy and at 6 months postpartum. To measure the influence of support on parenting outcomes, multi-level modeling was used to assess the Actor–Partner Interdependence model, which examines responses from both members of a dyad in a single analysis. Greater social support was associated with increased parenting self-efficacy (B = 0.062, p = 0.006) and parenting satisfaction (B = 0.111, p < 0.001). Higher family functioning was also associated with greater parenting satisfaction (B = 0.05, p = 0.035). Greater partner family functioning was associated with higher parenting satisfaction (B = 0.047, p = 0.026). This study found the importance of a strong support structure during pregnancy on perceived parenting competence in the early postpartum period for young mothers and fathers. Both social support and family functioning during pregnancy were associated with a greater sense of parenting competence, and these associations were mediated by parental depression. The results of this study underscore the importance of providing social support for young expectant fathers as well as mothers.