<p>Understanding how perfectionism and depressive symptoms develop together during adolescence is crucial for guiding early intervention and prevention efforts. This study therefore aimed to (a) identify distinct co-developmental trajectories of adolescent perfectionism and depressive symptoms across the high school years, and (b) examine whether parental perfectionism explains differences in these trajectories. A total of 1,110 adolescents were recruited from multiple schools and followed from Grade 7 to Grade 9; 1,055 (52% male, 48% female) completed the study. At Time 1, participants’ average age was 12.49 years (SD = 0.30). Parallel process latent growth curve modeling was used to examine three dimensions of perfectionism—rigid, self-critical, and narcissistic—alongside depressive symptoms. For rigid perfectionism and depressive symptoms, four trajectory classes emerged: Low-Increasing (24.2%), Low-Fluctuating/Stable (33.9%), High-Fluctuating/Stable (27.3%), and High-Decreasing (14.6%). Self-critical perfectionism and depressive symptoms also showed four classes: Moderate/Low-Increasing (22.7%), Curvilinear Perfectionism with High-Decreasing Depression (24.4%), Moderate Nonlinear-Increasing Perfectionism with High-Decreasing Depression (18.9%), and Low-Fluctuating/Stable (34.0%). Narcissistic perfectionism showed greater stability and weaker links to depressive symptoms, with three classes identified: High-Stable Perfectionism with Low-Increasing Depression (23.4%), Moderate/High-Decreasing (43.2%), and Low-Increasing Perfectionism with Low-Stable Depression (33.5%). Consistent with the goals of good health and well-being, the study reveals that parental perfectionism significantly predicted trajectory class membership across all perfectionism dimensions. This underscores the importance of family influences in shaping the joint development of perfectionism and depressive symptoms during adolescence.</p>