This longitudinal study investigated how attachment with mothers and fathers changes during adolescence, and how gender and parent–child relationship experiences are associated with attachment trajectories. The relative importance of specific positive and negative relationship experiences on attachment trajectories was also examined. An initial sample of 223 adolescents reported on relationship experiences and attachment avoidance and anxiety with mothers and fathers in Grades 6, 8, 10, and 12 (final N = 110; Mage = 11.90 years at onset, SD = .43). Mothers and fathers reported on relationship experiences with adolescents. Hierarchical linear modeling showed that security with parents increased during adolescence. Positive relationship experiences (companionship, satisfaction, approval, support) predicted increases in security, and negative experiences (pressure, criticism) predicted decreases in security. Females reported less avoidance than males.