Cost is the fundamental component for any construction project. While observations indicate that the cost overrun is a major phe­nomenon in construction industry worldwide. Hence, there are several factors responsible for cost overruns. So, a lot of studies have been conducted to investigate it. The aim of this paper is to identify the latest top major factors causing construction cost overrun construction projects in both of developed and developing countries (in particular) according to many variables during last three decades. through a comprehensive literature review, most common and frequently occurring causes of cost overrun worldwide and developing countries in particular were listed, factors were prioritized according to their occurrence, it is concluded that however cost overrun factors vary considerably across countries, the study of causing­ factors of cost overrun in construction projects will provide a reference for other projects that might be executed in similar circumstances and will also provide valuable information for international companies which intend to provide construction projects.