Abstract Millions of older adults receive care in intensive care units (ICUs) annually. However, the quality and accessibility of ICU-based palliative care is highly variable across hospitals and clinicians, due in part to specialists’ limited workforce and geographic inconsistency. Furthermore, there are few evidence-based interventions designed to help ICU clinicians provide primary palliative care themselves—and even fewer interventions tested among participants who adequately reflect the racial and ethnic diversity of the US. To address these gaps, we developed an innovative mobile app-based primary palliative care intervention called ICUconnect. ICUconnect facilitates families’ and patients’ self-report of actual palliative care needs across all core domains of palliative care quality, provides ICU clinicians with a scalable digital infrastructure for coordinating consistent and personalized needs-targeted care, and provides a variety of informational supports relevant to each user’s role. In a recent single-center cluster RCT with 111 patient-family member dyads (U54 MD012530), 42% of whom were Black, ICUconnect significantly improved unmet needs and goal concordance of care compared to usual care control. We have since linguistically and culturally adapted the intervention to Latin American Spanish. What is now needed is a multicenter RCT to test the intervention’s efficacy in a population diverse in race, ethnicity, and geography that reflects the real-world experience of patients and family members. Therefore, we propose to test ICUconnect vs. usual care control among 350 patient-family member dyads with elevated baseline levels of unmet palliative care need in a 4-site network serving a diverse population (Duke, Medical University of South Carolina, University of Alabama at Birmingham, Columbia). The specific aims are to: (1) Test the efficacy of ICUconnect vs. usual care control in improving palliative care needs and other person-centered outcomes including psychological distress, (2) Determine participant characteristics associated with a greater treatment response using a heterogeneity of treatment effects approach, and (3) Ensure off-the-shelf intervention readiness for implementation using a mixed-methods integration of qualitative analysis of semi-structured trial participant interviews and quantitative RE-AIM implementation framework-informed trial data. This project is likely to make a strong clinical impact because it fills notable gaps in the rigor of prior research, targets populations often omitted from past palliative care trials, and tests an innovative intervention that could be immediately used in any healthcare setting at population scale, is easily adaptable to any language, leverages strong preliminary data, and includes new concepts in care delivery and outcomes measurement. The likelihood of success is high because of the team’s expertise in clinical trials, critical care, palliative care, geriatrics, health equ...