Physical chemistry is a long-term precipitated product of interdisciplinary scientific research by numerous scientists in physics, chemistry, materials, and other disciplines. Scientists have demonstrated innumerable physicochemical properties of nanomaterials during energy and environment applications. Many physicochemical principles are also closely related to the preparation, characterization, and application of nanomaterials. In this chapter, we will discuss the physicochemical principles and case analysis of nanomaterials from the following eight branch aspects of physical chemistry: thermodynamics, kinetics, phase equilibrium, chemical equilibrium, electrochemistry, surface chemistry, colloidal chemistry, and theoretical chemistry. The summary of physicochemical principles of nanomaterials can provide atheoretical basis for energy and environmental applications.