Smartphones have become increasingly popular in recent years. However, it may be addiction-prone and result in negative outcomes. Given that relevant research remains limited, this study attempts to address two research gaps in the extant information systems literature. First, research on the determinants of smartphone addiction remains scarce. Second, the role of individual characteristics (i.e., gender) in the formation of smartphone addiction is far from clear. To fill these research gaps, this study develops a research model of smartphone addiction from the functionalist perspective and highlights the moderating role of gender with the insight of social orientation. We propose four categories of motives, including enhancement (i.e., perceived enjoyment), social (i.e., social relationship), coping (i.e., mood regulation and pastime), and conformity motives (i.e., conformity). Empirical results from our online survey illustrate that perceived enjoyment, mood regulation, pastime, and conformity positively affect smartphone addiction, whereas social relationship has no significant effect. Moreover, we find that gender moderates the effects of perceived enjoyment, pastime, and conformity on smartphone addiction. We expect that this study can enrich the theoretical understanding of how motives play different roles in the development of smartphone addiction. Implications are offered for both research and practice. •We examine the effects of motives and gender differences on smartphone addiction.•We assess four categories of motives: enhancement, social, coping, and conformity.•The moderating role of gender is also examined.•All motives except for social relationship affect smartphone addiction.•Gender significantly moderates the influences of motives.