Polysaccharide from red seaweed Gracilaria folifera has an interesting functional property of antioxidant activity and prebiotic effect. A feeding trial experiment was directed to examine the effect of probiotic bacteria Bacillus vireti 01 microencapsulated with G. folifera polysaccharide against freshwater prawn M. rosenbergii. Three different feeding trials were conducted for 15 days. The first group contained prawns fed with commercial diet. The second group was comprised of Aeromonas hydrophila challenged prawns fed with commercial feed. The third group consisted of A. hydrophila challenged prawns fed with microencapsulated probiotic-polysaccharide. Survival percentage was significantly decreased in prawns of group2 as compared to that of group1 and group3 prawns (p < 0.0001). The immunological parameters and antioxidant activities (p < 0.001) were found to be increased in group three prawns which were fed with encapsulated probiotic-seaweed polysaccharide and challenged with A. hydrophila as compared to that of group1 and group2. Tissue necrosis, fused lamella, haemocyte infiltration and damage of hepatopancreas lumen and tubule were noted in group2 prawns. There was no histological changes were observed in group3 prawns in which the histological architecture was similar to the control group1. The results suggested that combination of encapsulated probiotic B. vireti 01 and seaweed polysaccharide as dietary feed showed an enhancement of immune response, antioxidant activity and disease resistant of M. rosenbergii against A. hydrophila.