Objective: The study was designed to identify chronic effect of different doses (1/100LD50= 0.82 mg/kg and 1/50LD50= 1.64 mg/kgm) of Triazophos, O,O-diethyl-1-H-1,2,4-triazol-3-yl phosphorothioate, widely used organophosphorus pesticide (Ops). Materials and Methods: oxidative stress and plasma biomarkers of (liver, kidneys and thyroid) organs involved in xenobiotic metabolism. In addition to, histopathological examination. Results: The results revealed induction of oxidative stress, as evident by significant increase in malondialdehyde (MDA) level concurrent with reduction in total antioxidant capacity (TAC) in plasma of both TZ intoxicated groups. These observations were recorded following the inhibition of the plasma acetylcholinesterase (AchE) and ATPase enzymes biomarkers of Ops toxicity. Elevation in plasma liver biomarkers alanine (ALT) and aspartate (AST) aminotransferases activities in addition to total plasma protein were recorded in both intoxicated groups. Slight reduction in urea and creatinine plasma kidney biomarkers were recorded; However, significant elevation in plasma tiiodothyronine (T3) at p<0.05 and significant reduction in plasma (T4) was recorded in both intoxicated groups at p<0.01 and p<0.001 . Histoarchitecture of these organs confirms the above findings. Conclusion: The present study concludes that induction of oxidative stress that leading to subsequent alteration in liver, kidney and thyroid biomarkers and their histopathological architectures are an important mechanism in chronic TZ toxicity