This study aimed to understand the legal basis for PES in Indonesia and the possible challenges in its future implementation, to review relevant studies and summarize the findings into a PES database for Indonesia, and to observe a number of PES sites in the country. There are 14 policies and regulations related to PES in Indonesia. In some of the regulations, PES is explicitly written; in others, PES is either only implicitly noted or mentioned in different terms. Some regulations can be used for future PES implementation. Some supportive policies are already enacted; however, the important institutions needed to make PES operational are yet to be established through laws and regulations. The regulations to be enacted are as follows: regulatory agencies, agencies to establish the science of ecosystem services, third-party certifiers and verifiers, PES registries, and agencies providing market information to sellers and buyers. In this study, a total of 10 PES cases were selected from 91 operational PES sites for in-depth interviews. The database and results from the in-depth interviews were used to propose a re-definition of PES for Indonesia; to understand the current stages of PES implementation in the country; and to recognize the current actors, services, and payment schemes already in place.