Cooperative management of shared natural resources is one of the most urgent challenges the world is facing today. While there have been advances in understanding institutional design features that enable sustainable management, there are few field studies that provide theory-based insights into social psychological predictors of willingness to cooperate around shared resources. Here, we address this issue in the context of shared land management in pastoralist community conservancies in Kenya. In a large survey of individuals from different conservancies, we test a path model that links willingness to cooperate to how strongly respondents identified with their conservancy. This relationship is mediated by how efficient conservancies were perceived to be, and to what extent other people in the community were perceived to share cooperative norms. The results also point towards several parameters that may be conducive to developing stronger conservancy identification: transparency of purpose, motive alignment, sense of ownership, and demonstrating benefit. The findings provide insights into the social psychological processes that impact whether cooperative outcomes can be achieved in real-world shared resource settings, and offer practical implications for strengthening governance within pastoralist conservancies and related shared natural resource management contexts.