United States nonprofits are governed by boards of directors who have legal responsibilities based on the fiduciary duties of care, loyalty, and obedience. Boards, along with the chief executive, are held responsible to fulfill these standards which are designed to hold nonprofits legally accountable to carry out their tax exempt purpose by using organizational resources for the intended purpose, avoid conflict of interest, and ensure compliance. However, despite this weighty responsibility and the voluntary nature of nonprofits, no standardized process exists to educate nonprofit leaders about their legal responsibilities. While governance is a key area of nonprofit research, there is limited empirical evidence about how nonprofit leaders satisfy legal accountability demands. Using quantitative methods, this three paper dissertation establishes baseline data about nonprofit leader fiduciary knowledge, source of knowledge, and application of knowledge in their governance activities. A survey tool developed for this study yielded 186 responses from San Diego County nonprofit leaders. Using role and board service as the primary demographics, the results show that most nonprofit leaders believe they have enough knowledge of the fiduciary duties and frequently use their knowledge in the performance of their governance duties. However, when tested for actual knowledge, only 41% of board members and 70% of executives passed. When analyzed by board service, 56% of those who served on one to four boards in the past 15 years and 31% of those who have served on five or more boards passed. Further results show that nonprofit leaders were more likely to rely on informal sources of knowledge, such as conversations with their colleagues and other board members and less on more formalized sources, such as board orientations or a board manual, regardless of role or board service. Implications of this study point to the need for increased fiduciary duty knowledge amongst nonprofit leaders. Furthermore, this study can inform regulators, funders, and practitioners to develop standards and fund training to strengthen nonprofit accountability. As nonprofit leaders understand their fiduciary duties more fully, they are empowered to make decisions about organizational resources that uphold their legal responsibilities to carry out the mission.