The United Planters' Association of South India (UPASI), formed in 1893 at the zenith of British colonial rule in India, was an organization dedicated to the interests of British planters, mainly tea planters, of South India. In the first half century of its history, UPASI enjoyed an unusual degree of effectiveness and control. Its authority and reach owed to the fact that, unlike many other planters' organizations of the time, such as the Ceylon Planters' Association and the Planters' Association of Malay, UPASI was an “association of associations,” a cartel of cartels, its members being district associations. But its power also derived from the homogeneous ethnic composition of the firms that constituted and managed this body, making it an exclusive association of Europeans in an Indian world. In this article, I show how this combination of ethnicity and cooperation, dynamics that manifested across the entire range of modern businesses started in colonial India, proved to be both a source of strength and a point of weakness.