This study aimed to evaluate the susceptibility of whiteleg shrimp (Litopenaeus vannamei) to Vibrio parahaemolyticus,
a causative agent of acute hepatopancreatic necrosis disease at different salinities. Experimental shrimp were stocked at 40 individuals/tank containing 40 L of 15 ppt seawater. Salinities in the experimental tanks were adjusted to 10, 20, 25, 30, and 35 ppt, and remaining tanks (15 ppt) used as controls. The water temperature was maintained at 28°C. Three days after acclimatization to different salinities, shrimp were challenged with V. parahaemolyticus. Ten days after challenge, shrimp growing in 35 ppt salinity showed higher cumulative mortality than shrimp growing in 10 ppt. No significant difference occurred among the groups exposed to 15, 20, 25, and 30 ppt salinity. The median lethal time of challenged shrimp was 25.31 ± 4.06 hours at 35 ppt and significantly shorter than at 10 ppt (161.19 ± 4.60 hours) and at 15 ppt (91.30 ± 4.25 hours). The results suggest that whiteleg shrimp juveniles are more susceptible to V. parahaemolyticus when reared at 35 ppt salinity than at lower salinities.