According to J. Belsky's (1984) process model of parenting, both adolescents' and parents' personality should exert a significant impact on the quality of their mutual relationship. Using multi-informant, symmetric data on the Big Five personality traits and the relationship quality of mothers, fathers, and two adolescent children, the current study set out to test this prediction. Adolescents' agreeableness and parents' extraversion emerged as predictors of relationship warmth, whereas parents' openness emerged as a predictor of low restrictive control. In addition, some gender-specific effects emerged. Overall, parents' and adolescents' traits equally predicted the amount of relationship warmth, whereas adolescents' unique personality more strongly predicted the amount of restrictive control. The predictive power of adolescents' personality increased with age. Personality characteristics that affected relationship quality were partly shared between parents and their adolescent children. Findings support Belsky's (1984) notion that both parents' and children's personality predict the quality of their mutual relationship, though the relative predictive power of children and parents depends on the type of outcome variable and the age of the children.