Turkish DAP Project, as one of the major development schemes for the utilization of shared water resources, has brought about widespread environmental and legal consequences for downstream countries, particularly Iran. The impoundment the Karakurt, Tuzluca, and Soylu dams on the Aras River, in addition to severely reducing water flow, has led to environmental degradation, destruction of agriculture, and the drying up of vast areas in northwestern Iran. These actions constitute a violation of Turkey's international obligations within the framework of environmental and human rights conventions, as well as fundamental principles of international law the prohibition of harmful use of territory and the sic utere tuo ut alienum non laedas (no harm) rule.This article, using qualitative research methods of legal and environmental data, has examined the impacts of the DAP project on Iran's environment, especially concerning the reduction of water resources and environmental degradation, as one of its primary research objectives.