Previous research on sports rivalry has emphasized fans’ social identity and the threat posed by rivals. Much of this scholarship is based on intercollegiate sports, where many fans, such as students and alumni, have a formally defined identity with the university. In this study, fans (N = 4,828) across five major professional leagues—Major League Baseball (MLB), Major League Soccer (MLS), National Basketball Association (NBA), National Football League (NFL), and National Hockey League (NHL)—are surveyed to compare their animosity toward rivals based on four variables: schadenfreude, disidentification, prejudice, and relationship discrimination against rivals. The results consistently demonstrate that NFL fans harbor significantly greater animosity toward rivals than their counterparts in other leagues. Apart from the NFL, fans of NHL teams generally exhibit more animosity compared to other leagues, and NBA fans exhibit the least. While fan identification is relatively consistent across leagues, highly identified fans react more adversely to rivals. These differences in rivalry reactions have implications for promotional planning and event security protocol.