The effect of the probiotic, Leuconostoc mesenteroides B4 and its dextran product on growth performance of giant sea perch (Lates calcarifer) on field trial was investigated. Giant sea perch were fed control and L. mesenteroides B4 + dextran supplemented diets for up to 5 months, respectively. The results showed that in the 5th month of the control group, the harvest was 10,119 kg, percent weigh gain was 682%, the unit production was 44,125 kg/ha, the average fish body weight was 778 g, and the feed efficiency was 0.955. The fish harvest in the experimental pond was 10,195 kg, percent weigh gain was 699%, the unit production was 44,595 kg/ha, the average fish body weight was 784 g, and the feed efficiency was 0.965. This study showed that in the experimental pond with the probiotic L. mesenteroides B4 and its dextran product supplemented to the feed for the giant sea perch, the fish grew slightly faster than the control group, and the percent weigh gain was 699%, which was higher than the control group (682%) increased by 17%; and the unit production was 44,595 kg/ha, which was higher than the control group (44,125 kg/ha) increased by 470 kg/ha; the average fish body weight of the experimental group was 784 g, which was 6 g more than the control group (778 g), and the feed efficiency was 0.965, which was an increase of 0.01 compared with the control group (0.955). Overall, the results of this study indicate that dietary L. mesenteroides B4, and its dextran product could be an effective method for enhancing the growth performance in giant sea perch.