This is the first attempt to analyse the performance of US 12.6 million invested by Save The Tiger Fund (STF) in more than 250 tiger conservation grants in 13 tiger-range countries. We devised a simple implementation evaluation method to assess performance on an ordinal scale using archival documents from project grant files. Performance was scored based on whether the grantee managed to achieve what they set out to do as articulated in their project proposal. On average, STF grantee project outputs exceeded their original objectives, but many confounding variables made it difficult to determine the ecological outcomes of grantees’ conservation actions. Successful projects were usually collaborative in nature with high community visibility and support, their results were disseminated effectively, and they informed policy, measured outputs, were grounded by strong sound science, supported by government agencies, attracted new donors and delivered results even when political factors created difficult working environments. The poorly performing projects were associated with one or more of the following factors: poor tracking of results, deviation from the proposal, poorly defined goals, lack of capacity, poor evaluation practices, lack of political support, weak transparency, work at inappropriate scales or purchase of high-tech equipment that was never used.