This Practice Note describes the implementation of a partnership between child welfare and substance use providers in New York City, with the aim of supporting cross-systems collaboration and improving outcomes for dually involved families. Specifically, this report focuses on improving both coordination and communication between a preventive child welfare service provider (Montefiore Family Treatment & Rehabilitation Program), an outpatient substance abuse treatment provider (Montefiore Division of Substance Abuse), and the local department of social services (New York City Administration for Children’s Services). This article identifies general challenges with collaboration, describes how this collaboration was created and implemented in New York City, and provides guidance for other entities that are attempting to create similar collaborations.