Recently, silver nanoparticles (AgNPs) established a prospective value in aquaculture; however, extensive use afflicts fish and environment. Therefore, the current study represents a premier report to investigate the acute exposure of African catfish, Clarias gariepinus (B.) to AgNPs and the ethological alterations in a static renewal system. Additionally, AgNPs impact on blood profile, stress, brain activity, and branchial oxidative stress parameters were evaluated. Fish (50.71 ± 3.85 g) were exposed to different concentrations (0, 6.25, 12.5, 25, 50, and 100 mg L􀀀 1) of AgNPs for 96-h without water exchange. Finney’s probit analysis was used to estimate the 96- h LC50 value of AgNPs which recorded 21.38 mg L􀀀 1. In comparison to the control, the AgNPs exposed fish exhibited different ethological responses such as surfacing for gasping air, restlessness, slow swimming movement, aggressiveness, and nervousness and the scores of these behaviors and mortalities reached the high values with increasing AgNPs concentrations. There were marked reductions in hematological indices (RBCs, Hb, Hct, and WBCs), acetylcholine esterase (AChE) activity, and oxidative stress indices (superoxide dismutase (SOD), catalase (CAT), and reduced glutathione content (GSH)) of exposed groups in an AgNPs dose-dependent manner relative to the control group. On the contrary, the levels of stress-mediated indices (glucose and cortisol) and 8 hydroxy 2 deoxyguanosine (8OH2dG) were markedly decreased in all AgNPs exposed groups as compared with the control group and the reduction increased with increasing the exposure concentration. We concluded that AgNPs exposure of C. gariepinus induced marked alterations in behavior, blood profile, neurological, and branchial antioxidant parameters, and the 96-h LC50 of AgNPs was 21.38 mg L􀀀 1 and this provides a basis for future applying AgNPs as a safe therapeutic agent after considering the acute toxicity.