Objective: The authors compared symptom change trajectories and treatment outcome categories in children and adolescents receiving routine outpatient mental health services in a public community mental health system and a private managed care organization. Method: Archival longitudinal outcome data from parents completing the Youth Outcome Questionnaire (Y-OQ) were retrieved for children and adolescents (4-17 years old) served in a community mental health system (n = 936, mean age = 12 years, 40% girls or young women, 28% from families of color) and a managed care organization (n = 3,075, mean age = 13 years, 45% girls or young women, race and ethnicity not reported). The authors analyzed Y-OQ data using multilevel modeling and partial proportional odds modeling to test for differences in change trajectories and final outcomes across the 2 service settings. Results: Although initial symptom level was comparable across the 2 settings, the rate of change was significantly steeper for cases in the managed care setting. In addition, 24% of cases in the community mental health setting demonstrated a significant increase in symptoms over the course of treatment, compared with 14% of cases in the managed care setting. Conclusions: These results emphasize the need for increased attention to negative outcomes in routine mental health services and provide a stronger foundation for identifying youth cases at risk for treatment failure. In addition, given the overall differences observed across treatment settings for average rate of change and deterioration rates, results suggest that setting-specific model heuristics should be used for identifying cases at risk for negative outcomes. (Contains 6 tables and 1 figure.)