Formal private land conservation programs can be essential for achieving conservation goals, especially in ecosystems with substantial private ownership. Most deciduous oak woodlands in Humboldt County, California, and throughout the Pacific Northwest are located on private lands. The loss of these woodlands to conifer encroachment is a critical conservation concern, with implications for wildlife habitat, range management, cultural resources, biodiversity, and fire management. Private land programs depend on both incentives and voluntary cooperation. Through interviews and participant observation, we explored how and why landowners participate in oak woodland restoration. We are particularly interested in the role of social capital, which consists of trust and expectations of reciprocity. We found that oak woodland restoration depends on building social capital in order to leverage different skill sets and gain access to resources and technical expertise. Rather than a side effect of successful private land conservation, we assert that social capital is a necessary part of it, and that building and maintaining social capital can itself constitute a conservation goal.