To reduce the incidence of very long working hours, Korea is gradually implementing a major working-time reform, which lowers the statutory limit on total weekly working hours from 68 to 52 between 2018-2021. This paper provides a preliminary assessment of the reform with three key insights. First, the ongoing reform will bring Korea’s working time regulation in line with the dominant OECD practice. Second, the implementation of the 52-hour limit among large firms reduced the incidence of working more than 52 hours by 5 percentage points or about a fifth of its pre-reform level among employees working overtime. While these results are encouraging, they also suggest that working very long hours remains common, even among large firms that are subject to the new 52-hour limit. Third, two in five workers will remain exempt from the 52-hour limit once it is fully implemented in 2021. The main conclusion is that the reform represents an important step in the right direction, but that further efforts are needed to effectively change Korea’s long working-hour culture.