The purpose of this study is to examine the relationship between team members' aggressive communicative behavior and team relational conflict and whether team collectiveness mitigates the above relationship. The researchers expected, the more the team members use aggressive communicative behavior, the more relational conflict among team members will be aroused. But, the researchers also expected, in teams with high team collectiveness, the positive relationship between team members' aggressive communicative behavior and relational conflict in teams will attenuate. We designed a team collectiveness scale and tested its reliability and validity by 105 pre-test subjects. In the formal study, the researchers obtained an effective sample of 73 teams with 405 team members altogether. These teams came from 39 business organizations. And the response rate was 79% for teams and 74% for team members. The results of this study showed that the more the team members used aggressive communicative behavior, the more likely they perceive intragroup relational conflict. However, if the team members were equipped with high team collectiveness, the relationship between aggressive communicative behavior and team relational conflict tended to be weakened.