Institutions play a significant role in stabilising large-scale cooperationin common pool resource management. Without restrictions to govern humanbehaviour, most natural resources are vulnerable to overexploitation. This studyused a sample size of 336 households and community-level data from 30 communitiesaround Gonarezhou National Park in Zimbabwe, to analyse the relationshipbetween institutions and biodiversity outcomes in community-based wildlifeconservation. Our results suggest a much stronger effect of institutions on biodiversityoutcomes via the intermediacy of cooperation. Overall, the performance ofmost communities was below the desired level of institutional attributes that matterfor conservation. Good institutions are an important ingredient for cooperationin the respective communities. Disaggregating the metric measure of institutionsinto its components shows that governance, monitoring and enforcement are moreimportant for increased cooperation, while fairness of institutions seems to workagainst cooperation. Cooperation increases with trust and group size, and is alsohigher in communities that have endogenised punishment as opposed to communitiesthat still rely on external enforcement of rules and regulations. Cooperationdeclines as we move from communal areas into the resettlement schemes and withincreasing size of the resource system. A very strong positive relationship existsbetween cooperation and biodiversity outcomes implying that communities withelevated levels of cooperation are associated with a healthy wildlife population.Biodiversity outcomes are more successful in communities that either receivedwildlife management training, share information or those that are located far away from urban areas and are not very close to the boundary of the game park. Erectingan electric fence, the household head’s age, the number of years in school andnumber of years living in the area negatively affect biodiversity outcomes. Onepolicy implication of this study is to increase autonomy in CAMPFIRE communitiesso that they are able to invest in good institutions, which allows them toself-organise and to manage wildlife sustainably.