Using archival material from states, international organizations, and business actors, this paper explores how the Association for the Promotion and Protection of Private Foreign Investments (APPI), a transnational business interest association (BIA), liaised with different international institutions to lobby for better foreign investment protection. We zoom in on the United Nations, the Organization for Economic Co-operation and Development, and the World Bank to examine how APPI influenced the global institutional landscape during its heydays from 1958 until 1974. We show that business actors, particularly oil and banking corporations, created APPI as a nimble, efficient alliance that could move faster than existing BIAs. We further demonstrate how companies “forum shop” between different BIAs, and how APPI injected its ideas into the policymaking process, using the framework of the three faces of power. By shedding light on the role private business actors played in foreign investor protection, the paper contributes to a better understanding of the emergence of global economic governance in the second half of the 20th century.