Excessive self-disclosure online may risk the reputations, mental health problems, and professional lives of nursing students. This study investigated nursing students' usage of social media, their attitudes towards social media, mental health problems and self-disclosures, and the relationships of these variables. A cross-sectional study was conducted online (n = 1054) with questionnaires of Fear of Missing Out (FoMO), Social Media Fatigue (SMF), Students' Uses and Views of Social Media (SUVSM) and self-disclosure in social media which included self-information shown on social media and information viewed by others. Although most of them held positive attitudes towards social media, 17.4% of the participants acknowledged that they had posted inappropriate contents online and 37.6% witnessed improper posts from schoolmates or teachers online. SMF was affected by familiar with relevant regulations on the social media usage (β = -.10, p < .001), FoMO (β = .41, p < .001), and SUVSM (β = .17, p < .001). Additionally, nearly 1/3 participants reported their net-friends could view following information: gender, age, occupation, education level and location. Self- disclosure in social media was positively influenced by education (β = .10, p < .001), sharing moments or Weibo, etc. (β = .009, P = 0.009), time spent on social media daily (β = .11, p < .001), accepting stranger's "friend request" (β = .06, P = 0.047), FoMO (β = .14, p < .001) and SMF (β = .19, p < .001). Furthermore, effect of SUVSM on self-disclosure in social media was mediated by FoMO and SMF. Inappropriate contents are posted and witnessed by appreciable proportions of nursing students. Positive attitude towards social media may strengthen FoMO and SMF, which may increase self-disclosure in social media in turn.