To reveal the interests of actors in forest governance, this paper proposes a power-based interest identification (PII) approach. Based on the assumption of intentional action, the benefits that actors derive from policy impacts are the result of interest-driven actions. This paper further proposes a theoretical definition of interests that includes formal goals at the social and ecological levels, as well as informal political, economic, and strategic interests. Researchers need to identify powerful actors by identifying power mechanisms and resources, and can then observe actors' formal goals through interviews and documents. For informal interests, the actor observes the informal gains of powerful actors in policy impacts, which are then coded according to political, economic, and strategic interests. Combining these steps, actors can infer the formal and informal interests of powerful actors. • Researchers can verify actors’ formal objectives by interview and documents. • Among policy impacts, researchers can observe influences at the social and ecological levels, as well as changes in actors' control, economic gains, and dissemination of ideas. • Researchers can infer informal interests of powerful actors from observation of policy impacts.