Abstract: Cultivation of white leg shrimp Litopenaeus vannamei has been faced to unprecedented disease and environmental issues. This study was conducted to determine the effect of heat-killed Lactobacillus plantarum strain L-137 (HK L-137) on growth performance and immune responses of L. vannamei via dietary treatment. Different levels of 20% HK L-137 (LP20) were added into a commercial feed including 0.0g of LP20 kg-1 of feed (control), 0.1g of LP20 kg-1, 0.05g LP20 + 5g β-glucan kg-1 and 10g β-glucan kg-1. Shrimp (PL12) were fed with these feeds for 90 days in re-circulation 2 m3 tanks at stocking density of 300 ind./tank. The results showed that survival and growth rates of shrimp fed with feed supplemental LP20 were significantly (P<0.05) higher compared to other feeds. Immune parameters consist of total haemocyte count, differential haemocyte count, phenoloxidase activity, phagocytic activity and clearance efficiency, Vibrio parahemolyticus challenges were increased significantly (P<0.05) for those animals fed with HK L-137. This study demonstrated that HK L-137 would enhanced growth performance and improved immune defense system of L. vannamei.