Collaborations between nonprofit and public sector organizations have become an increasingly important phenomenon in state and local public service delivery since the publication of the Winter Commission report in 1993. This article focuses on one of the less studied types of public–nonprofit collaborations, those in which philanthropic support from nonprofit organizations supplements the resources and activities of public agencies. Drawing on the case of “nonprofit-as-supplement collaborations” that support park services in New York City, this article documents the benefits and drawbacks associated with such collaborations. While they can provide increased resources and encourage management innovations, they also can lead to inequities in the availability and quality of services, the preponderance of particularistic goals over the broader public interest, and the politicization of previously bureaucratic decision making. The authors offer two strategies for public managers to realize more effectively the benefits yet mitigate the shortcomings of these collaborations.