Childhood and adolescent bullying victimization procures mental health issues and dysfunction. Using a longitudinal design from the McMaster Teen study dataset, a semi-parametric group- based trajectory analysis was used to identify distinct patterns of peer victimization across ages 10 to 18. A three-class solution of peer victimization was selected. Most individuals followed a low decreasing trajectory of peer victimization (71.3%). The next largest group followed a moderate decreasing peer victimization trajectory (25.2%), and the smallest group followed a high stable peer victimization trajectory (3.5%). These trajectory groups were used to predict Borderline Personality Disorder (BPD) symptoms and Post-Traumatic Stress Disorder (PTSD) in emerging adulthood (ages 19 to 22). Results indicated that the high stable and moderate decreasing groups differed from the low decreasing group on BPD symptoms; individuals who were bullied by their peers in childhood and adolescence were more likely to have elevated symptoms of BPD in adulthood. However, when controlling for gender and childhood maltreatment, this differentiation only held true for the high stable group. Results also indicated that children and adolescents who followed a high stable trajectory of bullying victimization were more likely to meet PTSD diagnostic criteria in emerging adulthood than those who followed a low decreasing or moderate decreasing trajectory. The implications of the positive associations of childhood and adolescent bullying victimization on BPD symptoms and PTSD are considered via a group socialization theory lens. High levels of bullying victimization are explained as a form of relational trauma. Results suggest that peer relations are powerful enough to lead to subsequent personality pathology, and implications of these associations are examined through a developmental trauma framework. Understanding the developmental impact of childhood and adolescent bullying on BPD symptoms and PTSD provides insight and supports prevention and intervention initiatives at the school level and in clinical practice.