This study examined the longitudinal associations among maternal warmth, adolescents' self-disclosure, and maternal knowledge during the transition to adolescence. Three years of self-report data were collected from 131 married mothers and their adolescents. Results from longitudinal analysis using adolescent reports indicated that greater maternal warmth in sixth grade predicted higher levels of adolescents' self-disclosure in seventh grade, which in turn led to higher levels of maternal knowledge in eighth grade. Thus, adolescents' self-disclosure served as an indirect link between higher maternal warmth and greater knowledge over time. An alternative model with prior self-disclosure predicting subsequent maternal warmth and knowledge was not supported. Overall, this study demonstrated a time-ordered process by which maternal warmth and adolescents' self-disclosure predict maternal knowledge. Understanding such processes that affect parental knowledge may be beneficial for future prevention and intervention efforts during the transition to adolescence.