Diazinon, an organophosphate insecticide has been used in agriculture for several years. The aim of the present study was to analyze the hematotoxic effects of diazinon (DZN) at different time intervals (10, 20 and 30 days) on adult male albino rats. The changes in some hematological parameters; RBCs count, Hb content, Ht%, RBCs indices, total and differential count of WBCs, Platelets count, PT, APTT and bleeding time; were investigated. The antioxidant system in RBCs membrane; GSH, GST, GR, GPx, CAT and SOD; as well as LPO, as oxidative stress marker, were estimated. The current study showed that; DZN (14.88 mg/kg b.w.) at different time intervals resulted in decline in RBCs count, Hb content, Ht value, total WBCs count, platelets count, and relative lymphocytes and monocytes counts when compared with their control groups. On the other side, DZN caused increase in MCV, MCH, relative granulocytes count, bleeding time, PT and APTT. Furthermore, DZN decreased the activity of erythrocyte antioxidant enzymes (GST, GR, GPx, CAT and SOD) and GSH level. On the other hand, DZN caused increase in LPO. Generally, these all changes were directly proportional to the development of intoxication time. So, the current research concludes that DZN has hematotoxic effects which appeared in time-dependent manner.