This study examines the imposition of anti‐dumping (AD) duties on imported products in Korea. We use panel data for Korean firms between 2000 and 2012 and estimate the firm‐level productivity of import‐competing firms before and after AD imposition. Using a difference‐in‐difference framework, we compare firm productivity changes in a treatment group that receives AD protection to a control group that does not. In contrast to recent findings on the effects of AD measures, we find that the average protected firms experience productivity loss during the AD protection period. Examining the changes in external market condition and internal resource allocation during the protection period, such loss appears to be more evident inside highly concentrated import‐competing sectors. Further, we find that protected firms are more likely to reallocate their resources abroad via FDI at the expense of domestic production and investment once they receive temporary protection.