SummaryBecause promotions are an important source of wage growth, we argue that the low incidence of promotions among part-time workers will contribute to the emergence of the part-time wage gap. We test this claim using Dutch employer-employee matched data. We find that the parttime wage gap is absent among young school leavers, but that it is well established among more mature workers. Moreover, we find that promotions account for a wage growth of about eight log points. Finally, workers in part-time jobs experience a lower rate of promotion relative to workers in full-time jobs.