Sport fans rarely attend sporting events alone. While traditional consumer and sport fan behavior research frequently segmented fans based on demographic characteristics, recent advances in understanding how sport fans co-create and co-consume sporting events provides substantial evidence that sports fans shouldbe examined as tribal groups. In this chapter, seven dimensions of sport fan tribalism are proposed and tested (membership; geographic sense of community; social recognition; shared rivalry; and shared knowledge of symbols, rituals and traditions, and people) with samples from top-level American college football (Division I American football) and the top level of professional Portuguese soccer (Primeira Liga). The results provide reliability and validity evidence in support of the seven-dimension scale. In addition, the structural testing of the scale highlights differences between tribal fans and their teams (relative to other teams) in terms of five behavioral intentions and two commitment- related outcomevariables. The implications of labeling sports fans at tribal, the use of the seven-dimension scale and the structural results are all discussed.