Prior research has demonstrated a direct relationship between loyalty and reasons for liking a particular sport team. The current study replicates and extends this line of inquiry by examining the mediating role of attachment, a process by which an individual moves from merely liking a team (attraction) to becoming loyal to a team (allegiance). Data (Collegiate N = 194; Collegiate and Professional N = 402, Favorite Sport Team N = 808) were collected to examine 13 benefits and attributes associated with liking a sport team, 3 attitude formation properties, and allegiance. A three-stage test of mediation using MLR revealed that attachment mediated the relationship between allegiance and Vicarious Achievement, Nostalgia, Star Player, Escape, Success, and Peer Group Acceptance. Results demonstrate that allegiance is the outcome of a process by which individuals develop stronger emotional reactions to, more functional knowledge about, and greater symbolic value for benefits and attributes associated with a sport team.