Given minority patients' unequal access to quality care, patient activation and self-management strategies have been suggested as a promising approach to improving mental health care. OBJECTIVE To determine whether the DECIDE (Decide the problem; Explore the questions; Closed or open-ended questions; Identify the who, why, or how of the problem; Direct questions to your health care professional; Enjoy a shared solution) intervention, an educational strategy that teaches patients to ask questions and make collaborative decisions with their health care professional, improves patient activation and self-management, as well as engagement and retention in behavioral health care. DESIGN, SETTING, AND PATIENTS In this multisite randomized clinical trial performed from February 1, 2009, through October 9, 2011 (date of last follow-up interview), we recruited 647 English- or Spanish-speaking patients 18 to 70 years old from 13 outpatient community mental health clinics across 5 states and 1 US territory. A total of 722 patients were included in analyses of secondary outcomes. INTERVENTIONS Three DECIDE training sessions delivered by a care manager vs giving patients a brochure on management of behavioral health. MAIN OUTCOMES AND MEASURES Primary outcomeswere patient assessment of activation (Patient Activation Scale) and self-management (Perceived Efficacy in Patient-Physician Interactions). Secondary outcomes included patient engagement (proportion of visits attended of those scheduled) and retention (attending at least 4 visits in the 6 months after the baseline research assessment), collected through medical record review or electronic records. RESULTS Patients assigned to DECIDE reported significant increases in activation (mean β = 1.74, SD = 0.58; P = .003) and self-management (mean = 2.42, SD = 0.90; P = .008) relative to control patients, but there was no evidence of an effect on engagement or retention in care. CONCLUSIONS AND RELEVANCE The DECIDE intervention appears to help patients learn to effectively ask questions and participate in decisions about their behavioral health care, but a health care professional component might be needed to augment engagement in care. DECIDE appears to have promise as a strategy for changing the role of minority patients in behavioral health care.