Background <p>Coordinated specialty care (CSC) models for first episode psychosis include evidence-informed family education and support as a core component of care. Evidence suggests low rates of family engagement in many CSC programs. To address this gap, the FAMily Motivational Engagement Strategy (FAMES), a culturally responsive intervention, was previously developed, pilot-tested, and found to positively impact family engagement in CSC. The goals of this Hybrid Type 2 Effectiveness-Implementation study are to investigate whether FAMES improves family engagement in CSC, assess activation of target mechanisms, and evaluate a Culturally Responsive Approach to Targeting Equity (CURATE) implementation package used to support the integration of FAMES in CSC.</p> Methods <p>A stepped-wedge trial will be conducted with nine CSC sites, each randomized to one of three waves. CSC sites will initially recruit participant dyads into an attention control condition (<i>n</i> = 225) followed by a separate cohort of dyads who will receive FAMES (<i>n</i> = 225). Primary (engagement) and secondary (perceived stress, anxiety) outcomes, as well as mechanisms (self-efficacy, connectedness, motivation) among family members will be assessed. Secondary outcomes will also include client-level outcomes such as symptoms and engagement. Guided by the Reach, Effectiveness, Adoption, Implementation, Maintenance/Sustainability extension framework for sustainability, implementation outcomes (reach, adoption, implementation, sustainability) will be evaluated using mixed methods.</p> Discussion <p>This study represents one of the first studies to test the effectiveness of a culturally responsive family engagement intervention in CSC settings, where service utilization disparities among families are present. Findings from this study have the potential to improve the impact of CSC for families and advance understanding of equity-focused implementation approaches to facilitate the provision of culturally responsive care in mental health settings.</p> Trial registration <p>ClinicalTrials.gov NCT06945055. Registered on March 24, 2025. <a href="https://clinicaltrials.gov/study/NCT06945055">https://clinicaltrials.gov/study/NCT06945055</a>.</p>