Sport team fans identify with a team and continually internalize their favorite team as part of their self-concept (Wann, Melnick, Russel, & Pease, 2001). However, individuals simultaneously act different from the group to fulfill a psychological need to be distinct and unique (e.g., Brewer, 1991). The majority of prior studies in sport consumption behavior have emphasized that the sense of belonging to a sport team significantly influences a fan’s attitude toward the team and consequent sport consumption behaviors. Beyond the fan-team relationship, there has been limited research on why an individual fan behaves differently from others in the group, specifically why and how sport fans assert their personal and collective selves while in groups. Furthermore, fans attach not only to their favorite sport teams, but also to a fan community which support the team. Under the optimal distinctiveness framework, group dynamics are conceptualized as perceived interchangeability of group inclusion to the same group and interindividual differences (Simon & Kampmeier, 2001). This notion highlights the opposing forces or needs between fan distinctiveness (FD), to be distinct from other group members, and fan inclusiveness (FI), to be similar to other group members, as mutual determinants of the interpersonal self. Thus, the purpose of this research is to explore the psychological mechanism through which sport fans in a fan group balance two conflicting needs of group dynamics to make a decision on team apparel consumption. This was accomplished through two studies. Study 1 employed a survey design to confirm the established evidence on the effects of team identification on team merchandise consumption behaviors in prior sport management studies. It also uncovered the role of group dynamics in sport fans’ team apparel consumption behavior. Findings of Study 1 showed that the mechanism of group dynamics was induced by a level of FI, FD, or both. With a sequential association from university identification (UID) to team identification (TID), the group dynamics were shown to significantly influence team apparel consumption behavior. Study 2 replicated the findings of Study 1 with undergraduate students and National Football League (NFL) fans across group contexts. Study 2 was implemented with the same measurement items to investigate whether the effect of group dynamics on team apparel consumption are moderated by social visibility as a situational cue as well as a boundary condition. Study 2 provided additional evidence of the mechanism underlying the impact of group dynamics on team apparel consumption across two different research contexts. The overarching theoretical implication is that the mediator (group dynamics) and moderators (social visibility and context) influence sport fans’ team apparel consumption behaviors. The pendulum effect between the opposing forces of FI and FD in terms of group dynamics provide an insightful idea to extend optimal distinctiveness theory (ODT) framework and advance the theory. FD and FI play a key role in predicting fan unique team apparel consumption behavior. Moreover, if one of the needs, either FD or FI, are too dominate, the pendulum effect will help balance the needs out. The existing concept of group dynamics explains why sport fans seek unique team products, but cannot account for the traditional perspective of TID to consumption behavior models. Therefore, the current findings further understanding of why and how individuals within a group of fans consume team products based on their unique balance between group inclusiveness and personal distinctiveness. The findings will provide practical guidelines for both teams and sports brand marketers to understand the desire of sophisticated consumers to signal their individuality and what products and services should be offered according to the context-specific need. / Tourism and Sport