Brief Summary: The study focuses on the application of risk-based decision-making principles in the appraisal phase of a seawater desalination plant project in Aqaba, Jordan. This research is, case study of the seawater desalination plant project in the Aqaba region under the state of uncertainty and risk-based decision making in the project appraisal phase by studying and identifying the risks arising in the appraisal phase. Problem of Study: The appraisal phase is a critical stage in the project lifecycle, where key decisions are made regarding project feasibility, design, and investment. By applying a structured approach to risk identification, assessment, and mitigation, a large part of the existing risks in projects are the result of previous decisions that did not take into account the impact of these decisions, and the risks that could result from them. Therefore, in many projects, risk-based decisions are not taken, especially in the project appraisal phase and before its start. The study, in this research, was endeavor to study risk-based decision-making in the case of the Aqaba desalination plant. Study Aims: The study aims to enhance the decision-making process and improve the overall project outcomes. The Methodology: The methodology involves identifying potential risks associated with the project, assessing their likelihood and impact, and developing strategies to mitigate or manage these risks. The study also considers the unique environmental, social, and economic factors specific to the Aqaba region, which may influence the project's risk profile. The rustle of this study will provide valuable insights into the application of risk-based decision-making in the context of seawater desalination projects, with implications for other similar projects in the region and beyond. Findings: The study shows, after defining the risks in the appraisal phase according to risk-based decision-making methodology, that the output of existing risks in the appraisal phase allows the project to be implemented based on the decisions taken on the risks. Recommendations and Future Works: The recommendations for the relevant agencies, especially the planning agencies and their subsequent implementations, to take this study in their considerations when they work to implementing this project, as well as taking the principles of risk-based decision-making into consideration in the other projects. Accordingly, the researcher looks forward to continue the research in the future for developing a matrix of risks-based decision-making to be applied on in the state's general policies. Keywords: Jordan, fuzzy, risk assessment, risk-based decision-making.