The purpose of this study is to analyze the level of development of Turkey, which is in the process of full membership, against member countries of the European Union, and to rank countries in terms of sustainable development indicators by using an integrated approach. Ranking of alternatives for several criteria is a multi-criteria evaluation problem. Ranking of countries in terms of several sustainable development indicators is a multi-criteria evaluation problem. In this paper, an integrated approach composed of Entropy and TOPSIS methods is used. Entropy method is an objective way for determination of criteria weights. TOPSIS method is one of the useful multi-criteria decision making techniques that is very simple and easy to implement, so that it is used when the user prefers a simpler weighting approach. The basic principle of TOPSIS method is that the chosen alternative should have the shortest distance from the ideal solution and the farthest distance from the negative-ideal solution. The positive ideal solution is a solution that maximizes the benefit criteria and minimizes the cost criteria, whereas the negative ideal solution maximizes the cost criteria and minimizes the benefit criteria. The integrated approach is applied to 28 European Union countries and Turkey with 19 sustainable development indicators. According to selected sustainable development indicators, Sweden is the most sustainable country among EU countries. Turkey is scored as 20th in sustainability development ranking of EU countries and Turkey.