Curcumin, a natural polyphenolic flavonoid extracted from the rhizome of Curcuma longa L., has many beneficial biological activities. However, there are relatively few reports of the effects of curcumin on pathogen infections. This study examined the effect of curcumin on a Vibrio vulnificus infection. The cytotoxicity of V. vulnificus to HeLa cells was significantly inhibited by curcumin (at 10 or 30 μM). To further examine the inhibitory mechanism of curcumin against V. vulnificus-mediated cytotoxicity, the level of bacterial growth, bacterial motility, cell adhesion, RTX toxin expression and host cell reactions were evaluated. Curcumin inhibited V. vulnificus growth in HI broth. Curcumin inhibited both bacterial adhesion and RTX toxin binding to the host cells, which can be considered the major protective mechanisms for the decrease in V. vulnificus cytotoxicity. Curcumin also inhibited host cell rounding and actin aggregation, which are the early features of cell death caused by V. vulnificus. In addition, curcumin decreased the V. vulnificus-induced NF-κB translocation in HeLa cells. Finally, curcumin protected mice from V. vulnificus-induced septicemia. In conclusion, curcumin may be an alternative antimicrobial agent against fatal bacterial infections.