Amid concerns over declining business dynamism and slowing economic growth, policy efforts to promote firm growth have intensified. This study examines changes in high-growth firms’ activities in South Korea and their impact on industry productivity growth. Using Business Activity Survey data from Statistics Korea, the analysis shows that over the past 15 years, high-growth firms’ activities have declined significantly, and the share of young firms has also decreased. Furthermore, a higher revenue share of high-growth firms within an industry correlates positively with total factor productivity (TFP) growth, driven by increased average firm productivity and improved resource allocation. These findings suggest that the decline in high-growth firms' activities may hinder overall industry productivity growth.