In recent decades, the pace of industrialization has caused an number of environmental problems. A considerable increase in the global energy demand is one of the most important problems in today’s world. In fact, fossil fuels are the main source of energy triggering the release of huge amounts of greenhouse gases into the atmosphere. Many efforts have been made by researchers to come up with different strategies to mitigate the global consequences of greenhouse gas emissions such as global warming. One of these strategies is to reduce the amount of greenhouse gas emited into the atmosphere. This study aims to select the appropriate sites for carbon dioxide underground storage facilities. The selection of the best sites for CO2 underground storage is very important from various perspectives of sustainable development to accelerate the commercialization of such facilities. In this regard, fuzzy-Delphi methodology was used to prioritize the most important criteria in the CO2 storage process. Nineteen sub-criteria were selected in the technical, health, safety and environmental (HSE), economic and social categories. Specialist questionnaires were prepared, considering all relevant scientific and technical aspects, and experts in the field were invited to participate in the survey. The results were analyzed using SPSS 25.0. According to results, Geology and Lithology, Caprock Permeability, Social Acceptance, Depth, Reservoir Permeability, and Porosity were determined as the highest priorities. Based on the results achieved, it can be concluded that technical criteria are of the highest importance in the site selection of underground carbon dioxide site selection facilities.