In recent years, REDD+ projects are introduced in many countries as their main strategy for forest management at the community level. REDD+ means “reduced emissions from deforestation and forest degradation, as well as the sustainable management of forests and the conservation and enhancement of forest carbon stocks in developing countries”. Although the success of the community forest management activities in REDD+ projects largely depends on active households’ participation in community forest management activities, empirical evidence on what determines households’ participation in community forest management activities is still limited. Therefore, this study fills this gap. It uses a REDD+ project in Cambodia as a case study. Data the researcher collected through household questionnaire surveys and interviews was analyzed using the social-ecological system (SES) framework. This study revealed that community members’ willingness to protect forest, financial incentives to communities from carbon credit sales, and social capital (between community members, community REDD+ leader, village chief, NGOs, Department of Environment officials and rangers) were found to motivate community members to participate in forest management activities (forest patrols and REDD+ meetings) at the community level.