Abstract-This longitudinal study aimed to identify child, socio-demographic, family, and relationship factors associated with children's teacher relationship quality trajectories over the transition from preschool into school. A community sample of 636 Australian children were assessed in preschool, the first year, and second year of formal schooling. Teachers at all three assessments reported on child-teacher relationship quality. At preschool, teachers and parents reported on children's mental health difficulties and prosocial skills, and parents reported on family socio-demographic characteristics, stress, parenting styles, and parent-teacher relationships. Findings from latent-class growth modeling identified a 1) stable-high and 2) a moderate/declining child-teacher relationship trajectory. Logistic regressions found the strongest predictor of belonging to the moderate/declining relationship trajectory was the presence of teacher-rated preschool mental health difficulties. Children exposed to hostile-ineffective parenting were also more likely to experience a moderate/declining trajectory, whereas girls and children with more prosocial skills at preschool were less likely to have a moderate/declining trajectory. For children considered at-risk at preschool due to early mental health difficulties, prosocial skills and parental warmth appeared to protect them from the moderate/declining child-teacher relationship trajectory. Findings suggest that early-interventions focusing on fostering prosocial skills and positive parenting styles may help improve child-teacher relationships over time.