Reduced glutathione (GSH) is the most abundant non-enzymatic antioxidant present in mammalian cells and the main intracellular defence mechanism against oxidative stress. This study investigated the effects of GSH on survival rate, mean body gain weight, feed efficiency (FE), phenoloxidase (PO) activity, superoxide dismutase (SOD) activity, acid phosphatase (ACP), alkaline phosphatase (AKP) activity, GSH peroxidase (GPx) and susceptibility to Vibrio alginolyticus when Pacific white shrimps (Litopenaeus vannamei) were fed with GSH-containing diets. GSH was added to diets at 0.10, 0.20 and 0.30 g/kg during the eight-week breeding experiment. Oral administration of GSH had significantly increased mean body weight gain, FE, PO activity, SOD activity, ACP activity, AKP activity, GPx activity and susceptibility to V. alginolyticus compared with those of the control group (p < .05). Results indicate that GSH exerts both growth-promoting and immunostimulatory effects on Pacific white shrimps (L. vannamei).