As public housing residents age in place, they require health and social services outside of those traditionally offered by housing authorities. A promising response to these emerging needs is for housing authorities to collaborate with local public health departments to deliver coordinated services to older adult residents. Aging residents' health needs include health promotion activities, preventive health services, health education, and mental health services, among others. From 2001-2004 the New York City Department of Health and Mental Hygiene (DOHMH) and the New York City Housing Authority (NYCHA) collaborated to implement the Senior Wellness Project. This outreach program integrated health and social services provided by DOHMH and NYCHA, and delivered these services to older adult residents on site in 21 New York City public housing developments. Services were rendered at senior centers located in the housing developments and in residents' apartments. The program also referred residents to community healthcare providers to address special needs such as addiction. This article retroactively applies a formal model for interagency collaboration, the Stages of Collaboration, to describe and analyze the process of collaboration between DOHMH and NYCHA. It identifies the successes and shortcomings of the collaborative process, and explores the theory that successful collaboration leads to inherent challenges for implementation. Recommendations are then made for other public housing and public health agencies that have considered collaborating to address the needs of public housing residents who are aging in place.