In recent years, INGO legitimacy has been subject to growing scrutiny from analysts and practitioners alike. Critics have highlighted a backlash against INGOs in the Global South, a growing mismatch between INGO capacities and contemporary global challenges, and diminishing support for norms such as democracy and human rights that underpin INGOs’ work. Though these problems have attracted significant attention within the academic literature, this article argues that existing explorations of INGO legitimacy have broadly conformed either to a top-down approach focused on global norms and institutions or a bottom-up approach focused on the local dynamics surrounding states and populations in the Global South. We suggest that this divide is is unhelpful for understanding the current predicament and propose a new approach, which pays closer attention to the interaction between bottom-up and top-down dimensions, and to historical context. This new approach can provide important insights into current debates about the future roles and internal structures of INGOs.