Metamisole sodium (MS), a pyrosilone derivate, is widely used non-opioid analgesic in veterinary medicine. This study evaluated the effect of different doses of metamisole sodium on serum urea, creatin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phophatase (ALP) activities and tissue malondialdehyde (MDA) and reduced glutathione (GSH) level in liver and kidney in mice. The study involved 32 Swiss Albino mice. Animals were divided into four equal groups. One group was left control the other three groups received 20 (Group 1), 50 (Group II) and 100 mg/kg (Group III) MS intramuscularly for 7 days. After a seven-day injection blood and tissue samples were collected from mice. Serum samples were examined for the determination of BUN, creatin, ALT, AST and ALP while tissue samples were evaluated for MDA and GSH levels. The high dose group (100 mg/kg) had higher concentrations of serum BUN, creatin, ALT, AST and tissue MDA but low concentration of GSH (p<0.05) when compared to other groups.