This article presents research designed to deepen understanding of institutional fossil fuel divestment, as one approach to addressing climate change. Since 2011, a growing global social movement has emerged focused on divestment of fossil fuel company holdings and reinvestment of those resources in clean energy. The study used a qualitative research design, employing a positive deviance approach and the Transtheoretical Model of Behavior Change (TTM), a well-established clinical psychology framework, to explore U.S.-based foundation leaders' readiness to pursue divestment. Investors have conventionally relied on fossil fuel holdings as investment portfolio mainstays. Therefore, leaders' divestment behavior constituted positive deviance: intentionally engaging in non-normative behavior intended to contribute to successful outcomes. The study examined leaders' motivations and actions in pursuing divestment, while simultaneously exercising their fiduciary (legal) duty to steward responsibly institutional assets. Research questions focused on the divestment behavior change process. Data collection and analysis were derived from two datasets: 34 foundation divestment commitment statements and semi-structured interviews with 18 foundation leaders. Findings included that leaders engaging in divestment may experience higher levels of satisfaction, pride, happiness, and engagement with organizational roles. Results yielded insights into organizational leadership, climate action, and utility of positive deviance and the TTM as research methods.