Sport fans who have formed strong connections to their favorite team may be termed loyal fans. One popular communication tool for such fans is Twitter, which has been found to be an important medium for sharing news and events, yet few studies have examined the moderating of Twitter use in a sport context. Adopting the relational approach examining the determinants of sport-fan loyalty, this study examined how Twitter use moderates the building of fan loyalty. Findings revealed that team attraction, team trust, and team involvement are positively related to team attachment. While team attachment was found to positively influence fan loyalty, sport fans’ Twitter use was found to significantly reinforce their loyalty. Specific implications for both theory and practice are discussed.