Children who are adopted from care are more likely to experience enduring emotional and behavioral problems across development; however, adoptees’ trajectories of mental health problems and factors that impact their trajectories are poorly understood. Therefore, we used multilevel growth analyses to chart adoptees’ internalizing and externalizing problems across childhood, and examined the associations between preadoptive risk and postadoptive protective factors on their trajectories. This was investigated in a prospective longitudinal study of case file records (N = 374) and questionnaire-based follow-ups (N = 96) at approximately 5, 21, and 36 months postadoptive placement. Preadoptive adversity (indexed by age at placement, days in care, and number of adverse childhood experiences) was associated with higher internalizing and externalizing scores; the decrease in internalizing scores over childhood was accelerated for those exposed to lower levels of preadoptive risk. Warm adoptive parenting was associated with a marked reduction in children’s internalizing and externalizing problems over time. Although potentially limited by shared methods variance and lack of variability in parental warmth scores, these findings demonstrate the deleterious impact of preadoptive risk and the positive role of exceptionally warm adoptive parenting on children’s trajectories of mental health problems and have relevance for prevention and intervention strategies.