Recent studies have increasingly examined how overeducation relates to job satisfaction, but few have explored the psychological mechanisms that explain this link. This paper addresses that gap by analyzing how overeducation is associated with job satisfaction among Chinese workers, with a particular focus on the mediating effects of self-esteem and self-efficacy. Using data from the 2016 wave of the China Family Panel Studies (CFPS), the analysis applies Ordinary Least Squares (OLS) regression to estimate both direct and indirect effects. The results show that overeducation is associated with significantly reduced job satisfaction, after accounting for individual, demographic, and work-related characteristics. Both self-esteem and self-efficacy are positively related to job satisfaction and serve as partial mediators in the relationship between overeducation and job satisfaction. Moreover, regional analysis indicates that the negative roles of overeducation are more significant in central and western China, with notable variation in the mediating roles of psychological traits.