THE POSSIBLE antioxidant role of Achillea millefolium L. (ACM) extract was investigated against mutagenecity and immunological disorders in irradiated human blood cultures. Peripheral blood samples were collected from healthy human volunteers then incubated in the prepared cultures. The whole blood was exposed in vitro to 3 Gy of γ-ray and then the blood was cultured with mitogenic stimulation and ACM extract at different concentrations (100 & 200μg/ml). After 72hr of incubation, cytokinesis-block micronucleus analysis (CBMN) and immunological parameters: Interleukin-8 (IL-8), interleukin-18 (IL-18), cyclooxygenase-2 (COX-2) and tumor necrosis factor (TNF-α) were investigated. At each dose point, the treatment of the blood with ACM showed a significant decrease in the incidences of micronuclei (one, two and three micronuclei). Also, there are amelioration in the levels of IL-8, IL-18, Cox-2 and TNF-α. The maximum protection effect according to the selected parameters was observed at 200μg/ml of ACM extract. The presented data suggested that ACM may play important roles as antimutagenic and antinflammatory protectors against radiation exposure.