The purpose of this research is to identify and rank the causes of delays in construction projects in Iran and on a case-by-case basis in the city of Shiraz. The financial problems of the employer have the greatest impact on the occurrence of delays and financial problems of the contractor, problems in obtaining permits, order of changes by the employer, changes and errors in the design, weak management of the contractor and insufficient experience of the contractor are in the next categories. In order to collect data, two library and field methods were used in this research. Collecting primary information through the study of relevant articles and oral surveys of activists and expert experts active in construction projects in the city of Shiraz, a list of the most important factors affecting the occurrence of delays in these projects, including the five main factors, rules and regulations, the employer , consultant, contractor and miscellaneous and uncontrollable cases identified and 85 factors and causes caused by these factors in delaying construction projects were determined and then using a questionnaire and analyzing the resulting data with SPSS software, the factors and factors identified in terms of The impact on the occurrence of delays is rated. The results showed that, respectively, the factors of employer, contractor, consultant, uncontrollable cases and rules and regulations have the most influence on the delay of construction projects in Shiraz city. The sudden increase in prices and the lack of stability in the currency market, materials and wages are the most effective components, and forced accidents and unforeseen conditions such as: floods, earthquakes, and corona are known as the least effective components in causing delays.