Using Conservation of Resources Theory (COR), the current study examined the relationship between exposure to trauma, resources, and behavioral health in a prospective longitudinal cohort of youth in a public behavioral health system. The sample includes 303 youth, aged 5-19, who had received 6 months of treatment-asusual in an urban, diverse public behavioral health system, and who had experienced at least one type of trauma. Youth entered treatment with an average of four types of trauma and five accessible resources. Consistent with COR, multivariate regression model results showed that both lifetime exposure to trauma and youth resources were significantly associated with behavioral health needs, upon entry to treatment and after 6 months of treatment. Losing resources over 6 months of treatment was associated with greater behavioral health needs, while maintaining or gaining resources over 6 months of treatment was associated with fewer behavioral health needs. This study highlights the need to explore resource gain and resource loss among clients with trauma exposure receiving services in a public system, further test COR-related hypotheses in treatment settings, and develop applicable, multi-level interventions.