Decision-making is an important part of daily and business life for both individuals and organizations. Although the multi-criteria decision-making methods provide decision makers the necessary tools, they have differences in terms of the assumptions and fundamental theory. Hence, selecting the right decision-making method is at least as important as making the decision. TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) method, which is one of the most widely used multi-criteria decision-making methods, has gained attention of researchers and thus various improved versions of the method have been proposed. This study considers the conventional TOPSIS method and experimentally displays the underlying reasons of the lacks of the conventional TOPSIS method by using a simulation technique. Detailed experimental analysis based on simulation with an application is used to reveal theoretical fundamentals of the TOPSIS method to better understand it and contribute to its improvement.