This chapter looks at the introduction and practice of HRM deployed in Korean companies since the Asian Financial Crisis and the relationship between HRM and labor unions. The limited evidence from recent surveys and studies suggests that new HRM practices employed since the 1997 Asian Financial Crisis may have contributed to the gradual decline in union density, from a high of 18.6 per cent in 1989 to 10.2 per cent in 2015. Analysis did not find systematic evidence that HRM has directly affected labor unions, except where there was a change in union status from union to non-union. These results echo other researchers’ conclusion that the effect of labor union substitution with HRM practice is a primarily US phenomenon. A review of the extant empirical studies shows that labor unions play different roles in the adoption of specific HRM/management practices, with various impacts on workers and gendered implications.