Today, medical tourism is one of the fastest growing sectors of the tourism industry around the world. Medical tourism can contribute to the sustainable development and economic dynamism of countries. Therefore, in this study, we prioritize the world’s leading countries in medical tourism for Iranians. First, five main criteria and 20 sub-criteria were selected, which are the reasons for choosing a country as a medical tourism destination. In this paper a combined fuzzy SWARA-PROMETHEE approach was used to prioritize tourism destinations. The acronym PROMETHEE stands for Preference Ranking Organization Method for Enrichment Evaluation method and represents an useful MCDA (Multi-Criteria Decision Analysis) tool. On the other hand, SWARA acronym means Step-wise Weight Assessment Ratio Analysis. The criteria were weighted using the fuzzy SWARA approach. In the following, using the PROMETHEE approach, we prioritized eight countries as tourism destinations, then we identified criteria related to sustainability of medical tourism destinations and prioritized medical tourism destinations using these criteria as the contributions of this paper. The weights obtained for criteria “Abilities of skilled staff,” “Applied medical equipment,” “Marketing capability,” “Type of service provided,” and “Application of information and communications technology” were 0.176, 0.232, 0.108, 0.395, and 0.089, respectively. The results show that medical tourism destination priorities for Iranians are India (Phi = 0.1396), Malaysia (Phi = 0.1128), Panama (Phi = 0.0976), Mexico (Phi = 0.0790), Singapore (Phi = 0.0096), Taiwan (Phi = −0.0442), Brazil (Phi = −0.1747), and Costa Rica (Phi = −0.2196), respectively. Negative Phi values indicate below average performance of those countries and positive Phi values indicate above average performance of those criteria. The results indicate that countries with negative Phi values should be strengthened relative to the improvement of some criteria.