For many patients, primary care is an appropriate setting for advance care planning (ACP). ACP focuses on what matters most to patients and ensuring health care supports patient-defined goals. ACP may involve interactions between a clinician and a patient, but for seriously ill patients ACP could be managed by a team. We are conducting a cluster randomized trial comparing team-based to clinician-focused ACP using the Serious Illness Care Program (SICP) in 42 practices recruited from 7 practice-based research networks (PBRNs). Practices were randomized to one of the two models. Patients are referred to the study after engaging in ACP in primary care. Our target enrollment is 1260 subjects. Patient data are collected at enrollment, six months and one year. Primary outcomes are patient-reported goal-concordant care and days at home. Secondary outcomes include additional patient measures, clinician/team experience, and practice-level measures of SICP implementation. This trial was designed and is conducted by the Meta-network Learning and Research Center (Meta-LARC), a consortium of PBRNs focused on integrating engagement with patients, families, and other stakeholders into primary care research and practice. The trial pairs a comparative effectiveness study with implementation of a new program and is designed to balance fidelity to the assigned model with flexibility to allow each practice to adapt implementation to their environment and priorities. Our dissemination will report the results of comparing the two models and the implementation experience of the practices to create guidance for the spread of ACP in primary care.