This paper proposes a research model for investigating the effect on fan satisfaction and fan loyalty of the three dimensions of the customer engagement construct on Mobile Instant Messaging Apps when they are used as Engagement Platforms in a conversational marketing approach. To test the hypotheses, a sequential regression model was implemented. A survey was conducted on fans of a famous football team in Italy that has recently decided to use WhatsApp (Mobile Instant Messaging App - MIM) to allow fans to communicate directly with football players. The results highlight the importance of emotional engagement on fan satisfaction and the role of behavioural engagement through the use of WhatsApp for enhancing fan commitment. Fans who are engaged and more satisfied thanks to the use of MIM apps can be ambassadors for the sport brand thus affecting the fan behaviour-based relationship performance and the support to the team. For this reason, sports team managers need to consider the MIM app as a tool that can increase fan engagement.