In this dissertation, I explore global diffusion, rationalization, and the role global professionals play within both these processes. The main question I explore in this dissertation is: What role do global professionals play in the global diffusion and rationalization of formal structures? Within global diffusion studies, professions and professionals feature prominently. However, the literature says little about how formal structures become rationalized or, in other words, the process by which organizations, principles, and practices are rationalized. In addition, the specific, concrete ways that global professionals contribute to and partake in this diffusion is left relatively vague. My dissertation fills this gap in the literature. To do this, I focus on the new global professional field of transitional justice and, specifically, the diffusion and rationalization of truth commissions, a main mechanism of transitional justice. I draw on ethnographic and archival data derived from a year of internship within a leading transitional justice organization that works on truth commissions. I discuss the unintentional role that values play in provoking global professionals to rationalize and the consequences this rationalization has had on the diffusion of truth commissions, the values and culture of the organization, and the identity of the professionals. Theoretically, the dissertation contributes to scholarship on global diffusion and global professionals, specifically world polity theory. Empirically, the dissertation illuminates possible pitfalls non-profit organizations may fall into that subvert their foundational values and therefore offers a different approach to understanding organizational 'failures' and their potential fixes. Throughout the dissertation, I hope to highlight the import of values, both in being a driving force behind social action and within organizations, particularly those with humanitarian objectives. I also aim to make clear the precariousness of values and thus the critical need to think seriously about how they can be maintained as organizations grow, mature, and diffuse principles and practices.