This paper examines the factors contributing to the growth of part-time work in South Korea from 2010 to 2024, during which the fraction of part-time workers doubled. A decomposition analysis suggests that changes in the workforce composition account for approximately 30 percent of this growth, primarily driven by workforce aging. However, the explanatory power drops to around 10 percent when excluding workers likely to participate in a government program providing part-time jobs for older workers. This limited explanatory power is attributed to substantial within-group increases and a declining fraction of young workers, partially offsetting the expansion of older workers. These findings suggest that further research is needed to investigate factors beyond compositional changes to explain the recent growth of part-time work in South Korea.