Breast cancer treatment strategy depends mainly on the receptor status. Our aim was to identify a herbal preparation, effective against breast cancer, irrespective of hormone sensitivity, and to understand its molecular mechanism. The rich antioxidant composition of Hawthorn ( Crataegus oxyacantha ) makes it a promising anti-cancer drug candidate. Polyphenol-rich methanolic extract of C. oxyacantha berry (M.Co) was found to be cytotoxic on hormone receptor positive (MCF-7) and triple negative (MDA-MB-231) breast cancer cell lines, at a dose (75 mg/ml) safe on normal cells. It could effectively inhibit tumor cell proliferation and arrest cell cycle at G1/S transition in both cell lines. Molecular targets were selected from different levels of canonical Wnt signalling pathway (such as autocrine and antagonistic ligands, receptor, effector, cytoplasmic components, downstream targets and pathway antagonist), since they are frequently found dysregulated in all breast cancers and their aberrant activation is associated with cancer stem cell expansion. M.Co could significantly downregulate the expression of Wnt pathway agonists and upregulate that of Wnt antagonists at transcriptional and translational levels, in both cell lines. To conclude, C. oxyacantha berry extract is effective against breast cancer irrespective of its hormone dependency and cancer growth inhibition at stem cell level can be expected.