OBJECTIVES: To assess the prospective associations between mother-adolescent and father-adolescent relationship quality and early sexual intercourse initiation (ie, ≤16 years) among a large sample of Dutch adolescents. METHODS: Two waves of data from the Rotterdam Youth Monitor, a longitudinal study in the Netherlands, were used. The analysis sample consisted of 2931 adolescents aged 12 to 16 years (Meanage@T1 = 12.5 years, SD = 0.61; Meanage@T2 = 14.3 years, SD = 0.60). Variables were assessed by means of self-report questionnaires. Prospective associations between mother-adolescent and father-adolescent relationships and early sexual initiation were assessed by logistic regression analyses, stratified by gender, controlling for various potential confounders. RESULTS: We found that only girls (not boys) having a higher-quality relationship with mothers were significantly less likely to have initiated early sexual intercourse between T1 and T2. Bivariate findings showed that both girls and boys having a higher-quality relationship with their father at T1 were significantly less likely to have engaged in early sexual intercourse between T1 and T2, but when assessed multivariately, these associations were no longer significant, neither for boys nor for girls. CONCLUSIONS: Our findings suggest that a higher-quality relationship between adolescents and their parents, especially between mothers and daughters, may help to protect against early sexual initiation. Pediatricians and other health care professionals should be able to explain to parents that early sexual intercourse initiation can be associated with negative health outcomes, but that parents can play an important role in promoting healthy sexual behaviors.