This study examines how school-based personnel (i.e., principals, assistant principals, and school social workers) defined and engaged in collective leadership to support undocumented students. This instrumental, comparative case study explores their roles, relational processes, and the extent to which school-based personnel's relationships expanded or inhibited advocacy and equity work. Findings showcase a continuum of collective leadership, role management, and boundary work that influence advocacy for immigrant students. This research expands understandings of collective leadership, decision-making, and engagement with immigrant students. Implications for a social justice-oriented collective leadership model are discussed.