The effect of a bopyrid isopod Argeia pugettensis, on the growth and reproduction of the Kuro shrimp Argis lar was investigated. A commercial caridean shrimp in the East Sea of Korea, A. lar, was sampled monthly off Pohang with a bottom trawl from July 2009 to June 2011. During the study period, 7,988 individuals were sampled. These shrimp were parasitized by a bopyrid isopod Argeia pugettensis. The overall infection rate was 3.3%, although it declined in the larger size classes. It did not change monthly. The carapace lengths of the host and parasite were positively correlated. There was a significant difference in growth between infested and non-infested shrimp. The infested shrimp also had a lower gonadosomatic index (GSI) and breeding rate. These results suggest that the parasites affected the growth and reproduction of Argis lar.