With the prevalence of mobile devices and access to social networks, an increasing number of people are playing mobile social network games. This type of game differs from traditional online games with new capabilities of convenient mobile use and access to social networks. Despite the popularity of mobile social network games, there are limited studies in this field. Particularly, there is a lack of understandings of players’ motivations to play the game, and what would make them invite others to join the game. Our study addresses this gap by developing a model to explain what motivates players to join the game and under what circumstances they are willing to invite others to join the game. The model is tested by survey. Our results show that mobility motivates players to enter the game and have recreational play, while desire for advancement, relationship building and escapism motivate them to high engagement play. Meanwhile, high engagement play is positively related to players’ intention to invite their social network friends.