Abstract: The experiment was conducted to examine the effects of dietary administration of probiotic SKT-b (Vibrio alginolyticus ) and oligosaccharide from sweet potato ( Ipomoea batatas L. ) on growth performance and immune responses of white shrimp (Litopenaeus vannamei). Shrimp (0.33±0.02 g) was fed with basal diet (control without challenge test (-) and control with challenge test (+)), supplemented with combination of probiotic and prebiotic (probiotic 0.5% + prebiotic 1% (A), probiotic 1% + prebiotic 2% (B), probiotic 2% + prebiotic 4% (C)) for 30 days of culture. After feeding experiment, five shrimp per tank were sampled for bacterial quantification and immunity determination. Then all the shrimp rest were challenged by infectious myonecrosis virus and V. harveyi. After 30 days, Daily Growth Rate (DGR) and Food Conversion Ratio (FCR) of the shrimp were significantly better in treatment B than the control but weren’t significantly different (p>0.05) in other treatment. Other than that, phenoloxidase (PO) activity and Total Haemocyte Count (THC) of the shrimp in all synbiotic treatments were higher from the control group. After co-infection challenged test, PO, THC and Respiratory Burst (RB) activity of the shrimp in all synbiotic treatments were higher from control (+). Besides that, lowest survival shrimp occurred in the control (+) was significantly different compared with all synbiotic treatments.