Although the negative effects of a sense of overqualification on organizations and individuals have been examined, it is debatable whether overqualified employees hide knowledge. Relying on the social comparison theory and psychological contract theory, this paper tried to investigate the non-linear relationship between perceived overqualification and knowledge hiding via psychological contract breach by surveying employees with bachelor’s degrees or above and eventually recruited 475 participants. The results indicated that psychological contract breach acts a partial mediating role in the inverted U-shaped (...) relationship between perceived overqualification and knowledge hiding, while leader-member exchange acts as a moderator. The finding manifests that overqualification encourages employees to hide knowledge, but their possibly vigorous aspects will be displayed when a certain limit is exceeded. This study benefits organizations by advising them to dialectically treat and properly place overqualified employees and contributes to the research on overqualified employees’ knowledge management by offering a new explanation and complete understanding of perceived overqualification and knowledge hiding, with specific focus given to the psychological states of employees. (shrink)