With the popularity of smartphone and their increasingly rich functions, people's attachment to their phones is increasing. While people enjoy the convenience that smartphone bring (eg, accessing information and socializing), it also leads to problematic smartphone use (eg, phubbing). Previous research has shown that boredom proneness can trigger phubbing. However, the underlying psychological mechanisms are not yet clear.To address this research gap, we surveyed 556 Chinese college students (Mage = 18.89 years, SD = 1.18) during the COVID-19 pandemic and all participants completed a self-report questionnaire. Drawing the Interaction of Person-Affect-Cognition-Execution model (I-PACE) for addictive behaviors, this study developed and examined a multiple mediation model incorporating boredom proneness, loneliness, fear of missing out (FoMO), and phubbing.(1) Boredom proneness could positively predict phubbing; (2) loneliness and FoMO mediated the relationship between boredom proneness and phubbing, respectively; and (3) loneliness and FoMO sequentially mediated the relationship between boredom proneness and phubbing.These findings are not only valuable for understanding the underlying mechanisms linking boredom proneness and phubbing, but also suggest that three types of interventions could be effectively used to decrease the risk of phubbing among college students, namely, reducing boredom proneness, relieving loneliness, and decreasing FoMO.