Abstract: This research aimed to investigate biological responses of humpback grouper (C. altivelis) supplied by synbiotic supplement, which are growth, digestive enzyme activity and health status. Probiotic applied was isolated from humpback grouper digestive tract and screened for amilolytic, proteolytic and lipolytic activities; while prebiotic was obtained from the extracts of sweet potato (Ipoemea batatas). The experiments comprised of four combination of synbiotics containing 1% probiotic candidate in treatment RM3, RM4, RM5, RM7 + 2% prebiotic and one control (without symbiotic) supplementation. Each synbiotic treatment was added with 2% egg white to bind all ingredients together. Completely randomized design with three replicates was applied for the experiment during 40 days rearing period. The result indicated that treatment with synbiotics were significantly different (p<0.05) in protein and total digestibility as compared to control group, whereas treatment RM4 and RM7 had the best result in weight gain (ΔW), specific growth rate (SGR), protein retention, feed conversion ratio, RNA/DNA ratio, in comparison to treatment RM3, RM5 and without synbiotic. Application of synbiotic treatment combination of 1% probiotic RM4 + 2% prebiotic also showed enhancement of digestive enzyme activity (amylase, protease and lipase), biochemical plasma (glucose and triglyceride) and haematology parameter (haemoglobin, hematocrit and phagocytic activity).