The number of breast cancer patients has increased worldwide so finding a new anti-cancer agent, especially from natural products, is still challenging. In this research, cardanol, a major compound from Apis mellifera propolis collected in Nan province, was focused. Cardanol was extracted and purified from propolis as previously mentioned. The obtained cardanol was proved by thin layer chromatography and mass spectrometry. Also, by MTT assay, the IC₅₀ value of cardanol for BT-474 was 15.57 ± 1.73 μg/ml. Due to growth curve, the inhibition of BT-474 by cardanol was dose dependent. The change between untreated cell line and treated cell line with 2x IC₅₀ value of cardanol was different after 24, 48, and 72 h incubation by 2 parameters. The first one was by morphology. Under a light microscope, it showed that the change in morphology of both cardanol treated cells and doxorubicin treated cells was similar. Cells lose the adhesion to substratum. Organelle condensation was observed. The second one was by cell death program. By flow cytometry, it showed that the mix between apoptosis and necrosis was analysed in both cardanol treated cells and doxorubicin treated cell line. However, due to the cell death percentage, it showed that cardanol was more effective in inhibiting the growth of BT-474 before 48 h inhibition. In the future, the change in gene expression will be observed both at transcriptional level by real time qRT-PCR and at the translational level by western analysis. Later, the mechanism model on how cardanol can inhibit the growth of BT-474 cell line will be predicted.