This article examines the leadership roles and practices of community school coordinators (CSCs) in three full-service community schools (FSCSs). FSCSs are designed to improve the educational experiences and outcomes of historically underserved students through expanded learning opportunities, integrated service provision, family engagement, and community development. Drawing on the concepts of cross-boundary and relational leadership, and data from a qualitative multiple case study, the article describes how the CSCs, licensed social workers, intentionally used communication as a tool to build trusting relationships with and among principals, teachers, families, and community partners. These cross-boundary relationships, in turn, facilitated the identification, maintenance, and distribution of resources and services that advanced the case schools' goals for student success and community development. The study thus underscores the importance of CSCs' cross-boundary and relational leadership for creating the partnerships essential for effective FSCSs.