Abstract: White Spot Syndrome Virus (WSSV) is one of the most devastating shrimp pathogen which causes up to 70-90% mortality in commercial shrimp farming. This study was aimed to evaluate the effectiveness of synbiotic microcapsule (Bacillus NP5 RfR and mannan oligosaccharide combination) feed supplementation on the immune responses and growth performance of WSSV infected Pacific white shrimp. Shrimps (4.411±0.395 g) were cultured and fed by pellet containing synbiotic microcapsule at different dosages for 30 days, i.e., designated as 0.5% (M1), 1% (M2), 2% (M3) (w/w) and without synbiotic microcapsule addition (negative and positive controls). The synbiotic was encapsulated by spray drying method. Challenge test was performed at 31st of cultivation day by performing intramuscular injection of WSSV filtrate (104 copies mL–1). Compared with control, the shrimp fed by M2 and M3 were found to have higher (p<0.05) value of Total Hemocyte Count (THC), pro Phenol Oxidase (proPO) and Respiratory Burst (RB) activity compared to positive control. The results showed that the Specific Growth Rate (SGR) of M1 and M2 were higher (p<0.05) than controls. Yet, the Feed Conversion Ratio (FCR) were lower (p<0.05) than controls. Above all, the survival rate of shrimps fed with microcapsule synbiotic were higher (p<0.05) than controls.