This study investigates the factors affecting cost performance of construction projects in Kelantan State located in the east-coast part of Malaysia. It draws on relevant previous research in the theory of work on cost performance. Thirty-three contractors companies with different working grades in the state of Kelantan were participated in the study. Data were collected from the contractors using a questionnaire survey. The results indicated that the success factors affecting the cost performances of projects obtained by the analyses are identified as project manager competence in works affecting cost performance wholly and commitment responsibilities of all participants and various teams to the project as the top priorities while presence of poor project specific attributes and not existence of cooperate and Ignorance and lack of knowledge in operating, techniques and decision by project manager are identified as the most important failure factors. Further, the analysis indicates that the common factors which affected the cost performance in construction projects are mostly caused of uncertainty as one of the most important factors affecting the performance of the projects followed by the economy condition change.