College students are currently facing various crises due to psychological issues, driving universities to prioritise their mental health. Perceived overqualification negatively affects students' well-being. Drawing on the person-organisation fit theory, we propose that perceived overqualification reduces students' organisational identification, study engagement, and personal accomplishment. Furthermore, serving as a student leader and the frequency of extracurricular activities (ECA) participation play moderating roles. We conducted a two-wave survey with 423 freshmen at a university in China. Results showed that perceived overqualification negatively affected all three outcomes. In addition, serving as a student leader mitigated the negative effects of perceived overqualification on organisational identification and personal accomplishment, whereas the moderating effect of the frequency of ECA participation was not significant. Nonetheless, a supplementary analysis found that when students participated in ECA related to social practice, their perceived overqualification enhanced their personal accomplishment. Finally, our theoretical contributions to the existing literature are discussed, and suggestions are proposed for universities to impede the harmful effects of students' perceived overqualification.