The success of the project is usually assessed through the achievement of time, cost and scope criteria or better known as an iron triangle. In the context of development projects, project impact achievements are important to project success criteria as well as iron triangle achievement. The achievement of the success criteria of the project is influenced by various factors that need to be identified by the responsible parties in managing the project. In this regard, project managers are seen to have the greatest responsibility capacity for the success of the project. Therefore, project managers need to understand the context of the project thoroughly in determining the success of the project. Therefore, personality factors are emphasized because they can reflect the individual's understanding and inclination towards his environment consistently. Therefore, this study was conducted to identify the extent of the influence of project managers' personality factors in determining the success of managing a development project. Quantitative studies were conducted using personality surveys based on the Five-Factor Personality Model and the perception of the effectiveness of managing the project. The study was conducted on all project managers working in the Implementation Coordination Unit, Prime Minister's Department with a total number of 80 people. The result of the study was analyzed using Pearson's correlation and multiple linear regressions to explain the influence of the project manager's personality on the effectiveness of managing the project. The results of the study found that consensus, prudence, extroversion and openness had a significant relationship in influencing the effectiveness of managing project by the managers. The analysis found that extroversion and consensus are the most dominant factor in determining the effectiveness of managing the project. Therefore, the personality characteristic factor of the project manager should be given special emphasis on determining the effectiveness of the success of managing development projects.