Objective: The role of preschool-onset (PO) psychiatric disorders as correlates and/or risk factors for relational aggression during kindergarten or first grade was tested in a sample of 146 preschool-age children (age 3 to 5.11 years). Method: Axis-I diagnoses and symptom scores were derived using the Preschool Age Psychiatric Assessment. Children's roles in relational aggression as aggressor, victim, aggressive-victim, or nonaggressor/nonvictim were determined at preschool and again 24 months later at elementary school entry. Results: Preschoolers diagnosed with PO psychiatric disorders were three times as likely as the healthy preschoolers to be classified aggressors, victims, or aggressive-victims. Children diagnosed with PO disruptive, depressive, and/or anxiety disorders were at least six times as likely as children without PO psychiatric disorders to become aggressive-victims during elementary school after covarying for other key risk factors. Conclusions: Findings suggested that PO psychiatric disorders differentiated preschool and school-age children's roles in relational aggression based on teacher report. Recommendations for future research and preventative intervention aimed at minimizing the development of relational aggression in early childhood by identifying and targeting PO psychiatric disorders are made. (Contains 4 figures and 1 table.)