This study examined the effect of dietary prebiotics and probiotics after 16 weeks, followed by 8 weeks of post feeding trial with the control unsupplemented diet on haematological and immune response against Aeromonas hydrophila infection in Channa striata fingerlings. Fish were raised on a 40% protein and 12% lipid feed containing three commercial prebiotics (β-glucan, GOS or galacto-oligosaccharide, MOS or mannan-oligosaccharide); and two probiotics- (Saccharomyces cerevisiae, Lactobacillus acidophilus), respectively and a control. Throughout the study, supplementation with dietary prebiotics and probiotics led to significant (P < 0.05) improvement in the red blood cells, white blood cells, packed cell volume, haemoglobin concentration and serum protein level and lysozyme activities; and these improvements were effective significantly (P < 0.05) when the fish were challenged with Aeromonas hydrophila at the dose of 2 × 106. The disease resistance against A. hydrophila was higher significantly (P < 0.05) in fish fed with probiotic feed supplements (L.acidophilus was highest) compared to prebiotics and control. The study is the first to report the absence of differences in sustaining the efficacies attained after intake of β-glucan, GOS and MOS upon post-feeding with an unsupplemented feed, over a prolonged period.