Valproate is a widely used drug against epilepsy and several other neurological disorders although it has deleterious hepatotoxic side effects. The current study was designed to test if agmatine as nitric oxide modulator has protective effects against valproate‐induced hepatic injury. Male Swiss albino mice were treated with sodium valproate (SVP) with or without agmatine for 7 days. Serum and liver samples were collected for analysis. Results have revealed that agmatine exerted hepatoprotective effects against SVP‐associated hepatic injury. Agmatine ameliorated SVP‐induced elevated serum biochemical markers of hepatic damage such as serum transaminases, alkaline phosphatase, γ‐glutamyl transferase, and lactate dehydrogenase. Histopathological examination of the liver showed improvement of hepatic lesions in case of agmatine treatment. Furthermore, agmatine attenuated oxidative stress and enhanced antioxidants in liver tissue. Agmatine inhibited the activation of nuclear factor‐κB and ameliorated the immunoexpression of inducible nitric oxide synthetase. This was accompanied by decrease in the level of inflammatory markers as nitrite/nitrate, tumor necrosis factor‐α, and interleukin‐6. These data provide new evidence of the hepatoprotective activity of agmatine against SVP‐induced hepatotoxic effects.