Indigenous peoples and the environment are two things that are difficult to separate, because they are interdependent. The regulation of environmental law in Indonesia and in the world generally regulates the protection of indigenous peoples’ rights of the environment. Over time, conflicts over the environment often occur due to the needs of development that exploit the indigenous peoples’ environment. The problem in this paper is to protect the rights of indigenous peoples and their customary environment based on the Principles of Free and Prior Informed Consent (FPIC). Based on FPIC principles, indigenous peoples' rights of their environment can be protected and it will not cause harm to the indigenous peoples. When governments and investors use the customary environment of the indigenous people for both public and economic development interests, they must pay respect and appreciation to the indigenous peoples in the using the environment based on FPIC principles. This research was conducted by analyzing the rules of law and the principles of law, and examining the relationship of environmental law issues and the regulations that exist. The conclusion of this paper is that the principles of FPIC is the concept of environmental protection on the rights of indigenous peoples which must be applied in the existing laws of environmental law in Indonesia to maintain legal certainty in protecting indigenous peoples' customary environment.