Thuja occidentalis (family: Cupressaceae) has been used as antiseptic, expectorant, diuretic and in the treatment of cancer and removal of kidney stones in different systems of medicine. The present studies were carried out on T. occidentalis leaves extract to evaluate the hematological and biochemical effects on rabbits. The animals were divided in to control (A and B) and treated (C and D) male and female groups (n=5). There was a slight decrease in Hemoglobin, Red blood cell count and Hematocrit/Packed cell volume values, while a significant increase in platelet count was observed in male and female treated groups. However, slight increase in total leukocyte count value in male treated group and decrease count with female treated group was also observed. Urea, Creatine phospho kinase, Creatine phospho kinase iso-enzyme, Direct Bilirubin, Gamma-glutamyl transpeptidase, Cholesterol and Albumin/Globulin ratio values were elevated in male treated group. While Phosphorus, Uric acid, Lactate dehydrogenase, Serum glutamic oxaloacetic transaminase, serum glutamic-pyruvic transaminase, Alkaline Phosphatase, Cholesterol, Triglycerides, High density lipoprotein, Low density lipoprotein, Very-low-density lipoprotein, Globulin and Blood Glucose values were found low. In female treated group almost same results were observed like male treated group except that hypoglycemic effect was more pronounced in female treated group. These findings suggested that when results of hematological and biochemical parameters of test groups (C & D) were compared with their respective controls (A & B), significant changes were observed which contributes towards the diversified therapeutic effect of T. occidentalis.