Nonprofit organizations and the social services they provide have often engaged the attention of organizational scholars and practitioners. There is also a general perception of nonprofits as agents of social development in cases of public service failure. However, with the proliferation of many small nonprofits, their capacity for effective service delivery has been debated. Some have proposed cross-sector organizational partnerships (CSPs) as a means of assuring service effectiveness; however, such initiatives have been limited and not well understood in Nigeria. This study used a qualitative case study approach to focus on a CSP involving a nonprofit vocational training institute and 4 multinational companies in Nigeria. A purposeful sampling method was used, which emphasized participant experience and knowledge relevant to the study. Data were obtained from organizational records and participant interviews from a sample size of 10. An open-system theoretical lens was used as guide to answer the research question about the key elements of CSPs that support social service delivery by nonprofit organizations in Nigeria. Data analysis included coding, categorization, patterning, detailed description, and interpretation of the data. Categorical elements that increased institutional capacity of nonprofits or facilitated partnership management and government policy were found to be the key support to social service delivery. The results clarify links between CSP and social service delivery, and potentially aid synergy of action across sectors, in advancement of policy formulation and social service delivery.