First-year college students' adaptation problems and related mental health have attracted researchers' attention. The current research focuses on the depressive symptoms of first-year college students and aims to explore the relationship between the neuroticism trait and depressive symptoms, the mediating effect of addictive use of social media, and the moderating effect of psychological resilience. Three-wave longitudinal data from 1128 first-year students at a university in Fujian Province, China, were collected within three months of their enrollment. PROCESS macro for SPSS with bootstrapping was used to test the model. Results showed that the prevalence of moderate to severe severity of depressive symptoms in first-year students was 10.28% (T1) and 11.17% (T3). Addictive use of social media (T2) plays a moderated mediator role in the relationship between neuroticism (T1) and depressive symptoms (T3) of first-year students. Specifically, a low neuroticism individual does not necessarily have a less addictive use of social media. Psychological resilience (T1) moderated the above mediation. Implications for research and practice are discussed.