Inefficient urban areas are one of the most important issues in the urban environment that lead to disorganization. These tissues face many problems such as impenetrability and instability, and it can be said that physical, social, cultural, and economic damages are clearly seen in these tissues. In this regard, urban regeneration as an approach to renovating old cities and reflecting on the idea of ​​neighborhoods, with a comprehensive look at urban issues and avoiding a one-dimensional view and moving towards creating sustainable neighborhoods can solve the problems of inefficient structures in cities. slow Urban regeneration policy aims to provide living conditions for city residents, despite the appropriate goals in this research, their realization undoubtedly depends on solving the challenges and problems.Therefore, the aim of the current research is to evaluate the causal model (cause and effect) of the challenges of re-creating the ineffective areas of Tehran metropolis. According to its purpose, the current research is applied and based on the method, it is descriptive and causal. The statistical sample of the research was formed by experts and specialists related to urban regeneration. In order to achieve the goal of the research, Delphi model and Fuzzy Dimetal technique were used. The results of the article showed that based on DR values, among the regeneration criteria and challenges, the challenge of lack of integrated management of urban regeneration with a score of (1.37) is the most influential (cause) of the challenge. In other words, this challenge lays the foundation for other challenges of regeneration of ineffective areas of Tehran. Safety crisis and low resilience with a score of (0.01) have been the most effective (disabled) challenge of re-creating inefficient areas of Tehran.Based on D R values, the challenge of not managing integrated urban regeneration was identified as the most important regeneration challenge