IT projects need engineers with various backgrounds to cooperate to build an IT system that satisfy the requirements of users given a limited expense and time. Such diversity of team members and the complexity of task naturally involve considerable amount of conflict among team members. High level of conflict among team members is known to be detrimental to the performance of the team. The purpose of this study is to examine the reasons for conflicts among team members in IT projects and to check how the level of conflict affects the performance of a project and the satisfaction of the members of the project team. To test the relationship, a survey on 166 participants in IT projects was conducted. The reasons for conflicts in IT projects were categorized into five types. The level of ambiguity was found to have a significant correlation with the level of conflict. And the level of conflict, in turn, is found to have a significant effect on the degree of satisfaction among team members and the project results. Based on the research results, it is suggested that a clear definition of tasks and their boundaries is required to reduce ambiguity and thus, the level of conflict and improve the level of satisfaction of IT project team members.