The digital revolution has transformed many offline retailers to perform their business activities online, resulting in tough competition in a dynamic marketing environment. A well-built, user friendly, and attractive e-commerce website will result in high traffic intensity and eventually impact the market position of the online vendor. Over the past few decades, a number of studies have been done to predict the key determinants of e-commerce system success. This chapter considers the criteria, namely system quality, content quality, use, trust, support, personalization, and electronic word-of-mouth. Evaluating objects based on a single criterion may pose to be subjective, which have shifted these decisions towards multiple criteria, and hence has popularized the concept of multi-criteria decision making (MCDM). This chapter combines Pythagorean fuzzy analytic hierarchy process (PFAHP) and complex proportional assessment of alternatives with grey relations (COPRAS-G), under multiple decision makers, to select the best e-commerce website from five alternatives.