OBJECTIVES: This study aimed at disentangling the effects of overtime hours from those of long workhours. For part-time workers, overtime work is not intertwined with long workhours as it is for full-time workers. Therefore, part-time and full-time employees were compared with regard to the association between overtime and well-being (fatigue and work motivation). Such comparisons may also shed more light on the psychological meaning of overtime work for part-time and full-time workers. METHODS: A survey study was conducted among a representative sample of Dutch employees (N=2419). An analysis of covariance was used to investigate whether the relationship between overtime and well-being differs between marginal part-time (8–20 contractual workhours), substantial part-time (21–34 hours), and full-time (≥35 hours) workers. Work characteristics (ie, job demands, decision latitude, and job variety), age, and gender were treated as covariates. RESULTS: No significant relationship between overtime and fatigue was found for any of the contract-hour groups. For the part-time workers, overtime was not related to higher work motivation, whereas for full-time workers it was. CONCLUSIONS: It is important to distinguish between overtime and long workhours, given the differential overtime–motivation relationship among part-time and full-time workers. This finding suggests that part-time employees work overtime for reasons other than motivation or that working overtime does not enhance work motivation for this group of employees. Overtime work seems to have a different meaning for part-time and full-time workers.