Public-nonprofit contracting for human services is complicated by the difficulty of fully specifying contracts in the face of complex human service delivery issues. To understand how public and nonprofit agencies resolve these complications while serving client populations effectively and meeting public accountability requirements, this article examines the following research question: given the complexity of human service delivery, how do public and nonprofit managers address the challenges of contract management? The study analyzes qualitative data from interviews and focus groups with managers from three San Francisco Bay Area county human service agencies and three nonprofit agencies contracting with these public agencies to deliver human services. Findings uncover the deeply relational and collaborative nature of human service contracting amidst technical challenges that reflect the underlying complexity of human service delivery. The results also show how public and nonprofit managers address these dynamics to inform the task of organizing and delivering human services.