Bryonia dioica Jacq. is a climbing perennial herb with tuberous roots which is widely used in traditional medicine in Algeria for the treatment of cancer. The present study aimed to evaluate the apoptogenic activity and phytochemical composition of the aqueous extract of B. dioica roots growing in Algeria. The cytotoxic effect of B. dioica aqueous decoction against breast cancer MDA‑MB‑231 cells was evaluated by an MTT assay. Apoptosis induction was assessed by an Annexin V‑fluorescien iosthiocyanate assay. Propidium iodide staining of cell DNA was used to assess the effects on the cell cycle. In addition to UV‑Visible (UV‑vis) analysis, the major compounds of the extracts were determined using liquid chromatography‑mass spectrometric analyses. Our results showed that the B. dioica aqueous extract induced cell death in a time‑dependent manner. The highest inhibitory effect was produced at concentrations of 50 µg/ml or higher after 72 h of treatment (91.15±0.71%). Furthermore, the extract induced apoptosis of MDA‑MB‑231 cells. At 250 µg/ml, 64.61% of the treated MDA‑MB‑231 cells were apoptotic. This was accompanied by cell cycle arrest at G2/M phase. The percentage of cells in G2/M increased from 15.7% (untreated cells) to 59.13% (50 µg/ml) and 58.51% (250 µg/ml). The UV‑vis absorption spectra of B. dioica aqueous extract showed two absorption bands characteristic of the flavonol skeleton; 350‑385 nm (Band I) and 250‑280 nm (Band II). Myricetin (2,5,7,3,4,5‑pentahydroxylflavonol) was found to be the major compound in the B. dioica aqueous extract. These findings suggest that B. dioica could be considered a promising source for developing novel therapeutics against breast cancer.