The physicochemical properties of the surface of membranes are very important to understand the relationship between the structure of the membrane and its properties and to guide the modifications of its surface. Furthermore, knowledge of these parameters is essential to evaluate their performance in different applications and in specific separation processes. Aspects of the surface of a membrane, such as composition, morphology, topography, charge, and biocompatibility, are related to membrane performance parameters, including rejection, permeability, and tendency to fouling, and can notably affect their properties and applications. Many types of surface characterization techniques can be applied to study the surface properties of polymeric membranes. In this chapter, we describe protocols for the analysis of two important surface properties: zeta potential and contact angle.