Introduction: Health centers around the world are facing significant pressures to increase productivity. Therefore, in order to improve the quality of services and to create competitive advantages in these centers, we need to implement lean principles. The purpose of this study was to identify and prioritize the key factors affecting the implementation of lean thinking in the field of health services. Methods: This research is a kind of applied-descriptive study that was conducted in 2019. The data collection procedure included a questionnaire, articles, as well as interviewing experts. The study population included 15 managers, specialists, and experts in the field of health in five medical centers in Isfahan. After reviewing the literature, 16 factors influencing the implementation of lean thinking in the field of health services were identified and the most important ones were screened using the fuzzy Delphi method. Then, using the DEMATEL technique, the internal relationships between these factors were investigated and the most important ones were identified and prioritized using the Analytic Network Process. Results: The results indicated that "active leadership", "infrastructure of health centers", "staff resilience", "clear goals", "investing money and time", " staff participation", "step-by-step approach", "training", "monitoring and executing audits" and "paying attention to the concept of team" are respectively the most important factors for the successful implementation of lean thinking in health services. Conclusion: In an effort to achieve success in implementing a pure system, health care organizations must strengthen leadership, provide the necessary infrastructure, and ensure adequate resource allocation. Management already needs to have clear goals in advancing projects. In addition, a step-by-step approach as an important way to improve project implementation can help to accurately understand the process of implementing pure principles.