Since the early 2000s, regimes and institutions of global governance have undergone a paradigmatic shift in their relations with multinational corporations. The United Nations, in particular, has increasingly embraced big business as ‘partner’ in humanitarian response and development with the establishment of ‘global public–private partnerships’ (GP3s). This article situates this emerging mode of global governance within the recent academic discussions on Global Constitutionalism from a critical political economy perspective, focusing on the case of the UN Refugee Agency’s GP3s in refugee protection and assistance. Critically inquiring into GP3s not only as informal global constitutional arrangements but also as a set of political relations, this article asks: what is the constitutional and political nature of UNHCR–business partnerships? What impacts, if any, do they have on the agency? And, what does this mean for understanding global constitutionalism? The article argues that UNHCR partnerships are constituted as asymmetrical political relations in terms of their distributions of power, benefits, risks and commitments, that they are having neoliberal-oriented constitutive effects on the agency and that these constitutional dynamics challenge the more mainstream and liberal-based conceptualisations, analyses and promotion of current global constitutionalism processes.