Breast cancer is the most prevalent cancer and one of the leading causes of death among women in the world.Plants and herbs may play an important role in complementary or alternative treatment. The aim of this studywas to evaluate the antioxidant and anti-proliferative potential of Urtica dioica. The anti oxidant activity of anaqueous extract of Urtica dioica leaf was measured by MTT assay and the FRAP method while its anti-proliferativeactivity on the human breast cancer cell line (MCF-7) and fibroblasts isolated from foreskin tissue was evaluatedusing MTT assay. Mechanisms leading to apoptosis were also investigated at the molecular level by measuringthe amount of anti and pro-apoptotic proteins and at the cellular level by studying DNA fragmentation andannexin V staining by flow cytometry. The aqueous extract of Urtica dioica showed antioxidant effects with acorrelation coefficient of r2=0.997. Dose-dependent and anti-proliferative effects of the extract were observedonly on MCF-7 cells after 72 hrs with an IC50 value of 2 mg/ml. This anti proliferative activity was associatedwith an increase of apoptosis as demonstrated by DNA fragmentation, the appearance of apoptotic cells inflow cytometry analysis and an increase of the amount of calpain 1, calpastatin, caspase 3, caspase 9, Bax andBcl-2, all proteins involved in the apoptotic pathway. This is the first time such in vitro antiproliferative effectof aqueous extract of Urtica dioica leaf has been described for a breast cancer cell line. Our findings warrantfurther research on Urtica dioica as a potential chemotherapeutic agent for breast cancer.