International Environmental law is governed by many universal principles and concepts. These principles are globally accepted and have been used time and again in various Jurisprudence across the world at different level. This paper basically aims to cover all the fundamental principles governing international environmental law. Fundamental principles discussed in the paper are sovereignty, precautionary principle, principle of good neighborliness and international cooperation, principle of preventive action, duty to compensate for harm, principle of common but differentiated responsibility, principles of sustainable development, polluter pay principle and public trust doctrine. All these are fundamental doctrines in evolution of environmental law.