In order to extend the shelf life of sliced raw flatfish, the antimicrobial effects of natural essential oil from mustard and a mixture of ginger and mustard essential oils were tested at various temperatures. In addition, volatile components of the mixed essential oils were analyzed using gas chromatography and gas chromatography mass spectrometry. The viable cell counts of Vibrio parahaemolyticus treated with mixed essential oils from ginger and mustard was 0.7-1.3 log CFU/g lower than those of other treatments during storage at $5^{circ}C$. During storage at $20^{circ}C$, the viable cell counts of V. parahaemolyticus, V. vulnificus 01, and V. vulnificus 02 treated with the essential oils increased slightly from 6.53-6.64 log CFU/g at initial stages to 6.77-7.72 log CFU/g after 24-hr of storage, however they were 1.38-1.97 log CFU/g lower than those of the control group (8.74-9.10 log CFU/g). These results show that the growth of V. parahaemolyticus and V. vulnificus inoculated on sliced raw flatfish could be inhibited by treatment with natural essential oils from ginger and mustard at $5^{circ}C$ of storage. However, the antibacterial effects of the essential oils on Vibrio species observed in this study were not sufficient to merit their use in sliced raw flatfish at temperatures exceeding $20^{circ}C$.