There is an increasing awareness that indigenous communities hold a key role in sustainable forest management in Indonesia. However, this awareness did not necessarily come with sufficient legal acknowledgement of the rights of indigenous people to have autonomy over customary forest. This research aims to fill this gap through an understanding of the socio-political development that led to the policy institutionalization of the customary forest. The findings show that discourses on indigeneity, human rights, agrarian reform, social justice, and sustainability advocated by a coalition of Civil Society Organization (CSOs), dominated the political arrangements of both policies. The exchange of resources such as expertise, network, and participatory mapping among the CSOs helped to overshadow the counternarrative of competing policy actors. This thesis contends that a mature discourse coalition was a major factor that empowered the CSOs to advocate their discourses and to convince other actors to support legal recognition of customary forests. Furthermore, several political conjunctures also paved ways for an enabling environment for policy institutionalizations of customary forests. These political conjunctures include such as land reform activism, agrarian constitutionalism, REDD+, AMAN’s endorsement on Jokowi, and the merge of the Ministry of Forestry and Ministry of Environment.