The survival of both indigenous peoples and much of what remains of nature lies in the ability of both sides to find common ground. However, parks and protected areas have become the focus of conflict between conservationists and indigenous peoples. This antipathy is based on differing views about the nature of human impact on the natural world and masks the strong potential for these two groups to work together. In this paper we provide a case study illustrating how effective such cooperation can be. The Kaa-Iya del Gran Chaco National Park and Integrated Management Area was designed and implemented as the result of a collaboration between the Wildlife Conservation Society and the Capitanía de Alto y Bajo Izozog, the organization representing the 10,000 Guaraní people known as Isoceños.