This study investigates the complex dynamics of team sports, with a focus on the role of team members’ impressions of each other. We propose a novel team building method that incorporates dynamic elements to promote team formation and development, based on these impressions. A web-based system was developed to manage these impressions and collect data. This data was then analyzed to evaluate the impact of these impressions on team performance. Two team sports with distinct characteristics, American football and basketball, were examined. The results revealed that mutual impressions among team members significantly influenced team performance. This study underscores the importance of the interplay of team members’ impressions in team performance.