Multi-criteria decision analysis (MCDA) is an umbrella term to describe a collection of formal approaches that take account of multiple criteria in helping individuals or groups explore decisions that matter. MCDA techniques are instrumentally used in making the decision on the development of the complex index. In this book, the author presents the applications of two MCDA techniques, Delphi and AHP in developing a priority-based index for urban sustainability assessment in Cambodia. The Delphi technique was conducted to develop consensus indicators whereas the AHP technique was carried out to prioritize the developed consensus indicators. These applications showed that Delphi played an important role to develop and validate the initial indicators. After initial indicators validated, this technique was also significant in analyzing the consensus (the agreement). Especially, the AHP technique played a significant role in prioritizing the developed consensus indicators. Based on the significance of these techniques, the author proposes a combined Delphi and AHP method to develop a priority-based index for urban sustainability assessment in Cambodia.