This study was designed to determine the preventive effects of rutin toward the hematological toxicity of the anticancerous drug, cytarabine, in vivo using Balb C mice. The analysis of blood showed that subcutaneous injection of 50 mg/kg of cytarabine during three consecutive days caused a significant myelosupression. Indeed, the number of red and white blood cells decreased significantly (p<0.05). Moreover, the amount of hemoglobin and the percentage of the hematocrit decreased remarkably (p<0.05). However, the intra peritoneal injection of rutin (100 mg/kg) during six consecutive days didn’t exert any toxicological effects and the number of red and white blood cells, the amount of hemoglobin and the percentage of the hematocrit remained the same as in the control. The combination of rutin and cytarabine, where rutin was administered to mice three days before and three days during cytarabine treatment, protected blood cells from a veritable toxicity. In fact, the number of red cells, the amount of hemoglobin and the percentage of the hematocrit were significantly higher. However, the number of white blood cells was slightly protected. On the other hand, the treatment with cytarabine alone resulted in an elevation of body temperature in mice which reached 39°C. While, the temperature of the group treated with the combination of rutin and cytarabine remained normal and did not exceed 37.5°C. The ability of rutin to reduce hematological toxicity induced by cytarabine may be an important therapeutic factor in the treatment of cancer.