BackgroundWith the popularity of mobile socialization, people have become more closely connected with their phones. While people enjoy the convenience that phones bring (e.g., accessing information and socializing), they also feel anxious about missing out on certain information. Previous researches have shown that fear of missing out (FoMO) can trigger depressive symptoms, however, the underlying psychological mechanisms are not yet clear. In addition, limited research has explored this issue in the context of mobile social media.MethodsTo address this research gap, we surveyed 486 Chinese college students (278 males and 208 females, mean age = 19.95 years, SD = 1.14) and all participants completed a self-report questionnaire including mobile social media-related FoMO scale, phubbing scale, social exclusion scale, and the patient health questionnaire-9. The data were analyzed by SPSS24.0 and the Process macro and developed a mediating and moderating model incorporating phubbing and social exclusion.ResultsThe results showed that (1) mobile social media-related FoMO (MSM-related FoMO) can significantly and positively predict depressive symptoms among college students; (2) phubbing partially mediates the relationship between MSM-related FoMO and depressive symptoms; (3) the direct predictive effect of MSM-related FoMO on depressive symptoms is moderated by social exclusion.ConclusionThese findings are not only valuable for understanding the underlying mechanisms linking MSM-related FoMO and depressive symptoms, but also contribute to the development of psychological intervention programs (e.g., interventions based on social exclusion or phubbing) aiming at reducing college students’ depressive symptoms.Supplementary InformationThe online version contains supplementary material available at 10.1186/s40359-023-01231-1.