Background: Urtica dioica is one of the medicinal herbs with many uses in treating various diseases. In some studies, its antiproliferative and apoptotic effects on cancer cell lines have been shown. Therefore, the evaluation of U. dioica effect was performed on KG-1 cell line for acute myelogenous leukemia (AML) for the first time in this study. Materials and Methods: KG-1 cell line was treated by various extracts (aqueous, hydroalcoholic, chloroform and ethyl acetate) of U. dioica aerial parts and roots in different concentrations. Metabolic activity of extracts on cell line was assessed by MTT assay. To evaluate the percentage of apoptotic cells, the flow cytometry was performed by FITC Annexin V-PI apoptosis detection kit in KG-1 cell line treated with root chloroform (UDC-R) and ethyl acetate (UDE-R) extracts. The results have been reported as percentage of cell viability and IC50. Results: Based on MTT results, the strongest IC50 in KG-1 cell line (219.361μg/ml) was related to UDC-R. The flow cytometric analysis showed that UDC-R and UDE-R in IC50 concentration induced early (53.6% and 57.4%, respectively) and late (27% and 33.2%, respectively) apoptosis in KG-1 cells after 24 hrs. The inhibition of cell proliferation by various extracts of U. dioica was dependent on concentration (p=0.000). Conclusion: Flow cytometric analysis confirmed that UDC-R and UDE-R extracts affect on proliferation reduction of KG-1 cells by activating the apoptotic pathway.