To find potential alternatives for certain conventional antibiotics, we investigated the effects of silver nanoparticles (AgNPs) synthesized using Moringa oleifera extract on serum biochemistry, immunological, inflammatory, oxidative, and histological alterations, and DNA damage in Oreochromis niloticus infected with Aeromonas hydrophila. For determining the concentration of AgNPs, 110 fish were used; 11 groups were challenged with Aeromonas hydrophila (each group = 10 fish) and exposed to different concentrations of AgNPs (0, 0.4, 0.8, 1.2, 1.6, 2, 2.4, 2.8, 3.2, 3.6, and 4.0 mg/L) as immersion. Another 360 fish were categorized into eight groups: G1 was non-infected with Aeromonas hydrophila and treated with 0 mg/L AgNPs, G2 was infected and treated with 0 mg/L AgNPs, G3, G4, and G5 were non-infected and treated with 0.4, 0.8, and 1.2 mg/L AgNPs, respectively. G6, G7, and G8 were infected and treated with 0.4, 0.8, and 1.2 mg/L AgNPs, respectively, for seven days. Infection with Aeromonas hydrophila significantly altered the health and reduced lysozyme, hepatic CAT, and hepatic SOD activity, and IgM, complement 3, total protein, albumin, globulin, serum nitric oxide, and IL-10 levels, with a significant increase in the activity of ALT, AST, LDH, and levels of urea, creatinine, bilirubin, hepatic MDA, and inflammatory biomarkers (IL-1β and IL-6). Moreover, the infection produced a prominent genotoxic effect and impaired the architecture of hepatic, renal, splenic, and gill tissues with a strong expression of NF-kB. Fish exposed to different treatments of AgNPs showed improvement in these markers with a significant reduction in the mortality rate. Interestingly, the submersion of infected fish in 0.8 mg/L AgNPs produced the best result. These results showed that green biosynthesis of AgNPs is non-cytotoxic and provides an alternative antimicrobial compound against hepatotoxic, splenotoxic, nephrotoxic, genotoxic, and immunosuppressive impacts of Aeromonas hydrophila in Nile tilapia.