BACKGROUND: Hypercholesterolemia is among the most common health problems treated with traditional remedies. Nigella sativa (NS) is an effective plant for treating hypercholesterolemia.However, the effects of this herb on hematologic factors and hemostasis system have not been elucidated.This study was designed to investigate the effects of NS on these factors in both normal and hypercholesterolemic rabbits.METHODS: In this research, twenty rabbits were randomly distributed into four groups of five.The groups received four different diets, namely normal, normal+NS (5%), hypercholesterolemic (1% cholesterol), and hypercholesterolemic (1% cholesterol) +NS (5%), for 8 weeks.After this period, WBC (white blood cell), RBC (red blood cell), HTC (hematocrit), HGB (hemoglobin content), PLT (platelet), fibrinogen (FIB) and factors VII (F VII) were measured.RESULTS: Using NS significantly increased PLT count in the normal group. In addition, it significantly decreased WBC counts in the hypercholesterolemic group (P<0.05). However, dietary use of NS did not have any effects on other hematologic factors including RBC, HTC, HGB, FIB, and F VII (P<0.05).CONCLUSION: Increased PLT numbers might cause enhanced coagulation. The achieved results call for more research on the effects of various diets (hypercholesterolemic and normal diet) supplemented with NS on different coagulation factors and hemostasis system.