Introduction: Among the 3.2 million Latinos in the United States with serious mental illness (SMI) in 2024, less than 15.5% received any treatment or medication. Research on mental health treatment engagement among Latinos has largely conceptualized engagement broadly, overlooking nuances in the engagement process, disorder severity, and community heterogeneity. Most studies on treatment engagement among Latinos with SMI have explored macro-level factors without a guiding framework or theory. Thus, the aim of the current study was to identify barriers to and facilitators of treatment engagement among Latinos with SMI using the Consolidated Framework for Implementation Research (CFIR). Methods: Sixteen Latino adults with SMI ( Results: Thematic analysis of the data identified a range of barriers to and facilitators of engagement in mental health treatment. Inner setting domain barriers included incongruence between treatment and Latino culture, and limited availability of bilingual and bicultural providers. Individual characteristic domain barriers included negative experience with mental health providers, lack of trust in providers and systems of care, and mental health stigma. Inner setting domain facilitators included mental health psychoeducation and providers who listen and are compassionate. Individual characteristics domain facilitators included preferences for behavior-based, context-based, and faith-based care. Conclusion: These findings contribute to existing literature by shedding light on non-social determinants of health (SDOH)-related barriers to and facilitators of treatment engagement for Latinos with SMI.