This paper analyzes the strategic role of the voluntary disclosure of private information about costs or willingness to donate in the context of fundraising competition between two nonprofit organizations. We examine how the incentives to disclose change when nonprofit organizations compete for donations instead of profits and how these decisions are shaped by whether donors perceive the organizations' projects as complements or substitutes. We analyze how disclosure decisions depend on the relative usefulness of the private information for the disclosing nonprofit organization (NPO) compared to its competitor. In settings where projects are viewed as weak substitutes or complements, NPOs always disclose their private cost information. They only disclose their willingness to donate information when it is symmetrically useful, enabling coordination and therefore softening the fundraising war. In contrast, when projects are perceived as strong substitutes, disclosure occurs when the information is asymmetrically useful for an organization. We illustrate how our results relate to earlier findings in the literature. Our research bridges the gap between strategic disclosure decisions of nonprofits in donative markets and for-profits in product markets.