Although part‐time employment often appears as a substandard form of employment, evidence that part‐time employees are less satisfied than full‐time employees is ambiguous. To shed more light on this puzzle, I test an extended discrepancy theory framework using data from the German Socio‐Economic Panel. The results help explain previous inconsistent findings: Part‐time employment increases the chances of being underemployed while it reduces the likelihood of working more hours than preferred, and the negative effects of both types of working time mismatches on job satisfaction are similar in size. Furthermore, the importance attributed to family roles mitigates the negative effect of part‐time employment on job satisfaction.