We use a randomized control trial to study whether an interest-based negotiation (IBN) training for community leaders in Liberia improves their ability to strike beneficial deals related to their land and forests. We use environmental assessments, lab-in-the-field, and surveys and find that trainees are 27% more likely to reach a beneficial agreement, and when they conclude deals, their payoffs are 37% larger. Our mediation analysis and structural estimates both indicate that IBN increases trainees’ capacity to identify positive-sum agreements. We also document a reduction (0.26 standard deviations) in the exploitation of communal forestland in trainees’ communities.