Abstract: One of the most important facets of managing a construction company is leadership. Although, the issue of leadership has been widely covered in management or business school, a lack of attention has been given in the field of the reconstruction industry. This study explores the effect of the project complexity on the relationship between the leadership and internal success of construction projects. Hypothesis testing in this study includes collection data of 172 operational and middle management managers from construction organization in Jordan. Then interpretation of with SEM-PLS for data analysis. Quantitative data were collected with distributing the questionnaires with hard copy and soft copy among the sample of analysis. Data were analyzed using descriptive statistics, reliability, correlation and structural equation modelling. The finding of the study demonstrates that there is a relationship between project management leadership style and the internal success of project, except the transactional leadership style. According to the study, transformational leadership has the most influence on internal project success. As well, it reveals that the project complexity as moderator does not have impact on internal project success.