This study showed the effects of propolis on biochemical and hematological parameters in chronic nitric oxide synthase inhibited rats by Nω-Nitro-L-arginine methyl ester (L-NAME). Rats are given L-NAME for 15 days and the propolis for the last 5 days with L-NAME together. The levels of aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase and gamma glutamyltransferase in the L-NAME group compared to control group have increased (P<0.05). The levels of these parameters in L-NAME+propolis group compared to the L-NAME group have decreased (P<0.05). L-NAME caused increase (P<0.05) in levels of glucose, albumin, globulin, creatinine, urea, triglyceride and cholesterol. Erythrocyte number, total leukocyte, hemoglobin, hematocrit, neutrophil and monocyte decreased (P<0.05), platelets and lymphocyte increased (P<0.05) in L-NAME+propolis group compared to the L-NAME group. The study concluded that homeostasis is modulated in L-NAME administrated rats by adding propolis which causes increasing generation of vascular nitric oxide.