Swiss trading houses enjoy 35% of global market share in crude oil. How can we explain the importance of Swiss traders in the global oil market? This article argues that Swiss trading houses are part of the private governance arrangements that emerged in response to the wave of nationalization sweeping across the worlds prime oil producers. As the global crude supply chains deverticalized following nationalization, companies created mechanisms to manage the problems of price-setting, and matching suppliers and consumers. By tracing state and private governance before and after the 1970 nationalizations, we show that the new model of oil market governance also aligned with the state goals of ensuring the reliable oil supply at adequate pricesenergy security. The article contributes theoretically to the scholarly debate on private governance, and to an emerging literature on the political economy of commodities. It also challenges the dominant state-centered approaches in the international political economy of oil. 2020, 2020 Informa UK Limited, trading as Taylor & Francis Group.