Board members play a significant, yet largely unexamined, role in nonprofit collaboration. Processes, such as finding prospective partners, creating common ground with a partner, and establishing appropriate collaborative governance implicate nonprofit board members. In contrast to the scholarship of the role of interlocking directorates as potential networks for nonprofit collaboration, this paper examines the role of board members' social and human capital on nonprofit collaboration with other nonprofits, businesses, and government agencies. Drawing on online survey data from 636 nonprofit organizations, this paper finds that board social capital—but not board human capital—is positively related to the presence and number of within‐sector and cross‐sector nonprofit collaboration. However, board human capital enhances nonprofit‐government collaboration, when board social capital is also high. The results provide a novel perspective in nonprofit collaboration and board management research.