This study drew on prospective, longitudinal data to test the hypothesis that the intergenerational transmission of positive parenting is mediated by competence in subsequent relationships with peers and romantic partners. Interview-based ratings of supportive parenting were completed with a sample of 113 individuals (46% male) followed from birth to age 32. Results indicated that supportive parenting during adulthood was predicted by observed maternal sensitivity during the first 3 years of life, even after controlling for adults' age at first childbirth and adults' socioeconomic status and educational attainment at the time of the second generation parenting assessments. Moreover, the intergenerational association in parenting was mediated by later competence in relationships with peers and romantic partners. In particular, sensitive caregiving in infancy and early childhood predicted teachers' rankings of children's social competence with peers during childhood and adolescence, which in turn forecasted later interview ratings of romantic relationship competence during young adulthood, which in turn predicted supportive parenting in adulthood. Findings are discussed with respect to current theory and research on the intergenerational transmission of parenting.