Nonprofit social capital refers to the trust, norms, and networks that can improve organizational performance to fulfill a mission. Research on social capital within organizations, and specifically with nonprofits, is relatively widespread; however, the notion that we can quantify, measure, and incentivize its growth across a sector is novel. Nonprofits actively work to solve some of society’s most complex challenges in diverse areas, such as public health, education, social inequality, and environment. Few would argue against the need for a robust and healthy nonprofit sector. Yet, there is little debate and even less agreement on the definition of “a healthy nonprofit sector” or how to measure it. We offer a policy brief on this topic in the form of an exploratory think piece, rather than a definitive empirical methodology or research paper, that connects nonprofit social capital to a framework of sector health. Solving many of the challenges facing society today will require trust, working together, and networks of resources and reciprocity. Because of this, nonprofit social capital – both cognitive and structural – is an important benchmark of nonprofit sector health and could supplement other metrics of an index offering a signal as to changes occurring in the sector.