Tarantula cubensis Alcoholic Extract (TCAE) is a homeopathic agent used for treating many disorders. This study aimed to define the effects of TCAE on the breast carcinoma cell line (MCF-7). After various concentrations (10, 20, 40, 80 and 160 μl/ml) of TCAE were applied to MCF-7 cells and the human embryonic kidney cell line (HEK293), the cells were incubated for 1, 3, 6, 9, 12, 24 and 48 h, followed by analysis by MTT assays. According to the results of the MTT assays, cells treated with 20 or 40 μl/ml TCAE for 6 h were applied to apoptosis analysis by flow cytometry. Secreted levels of tumor necrosis factor alpha (TNFα), interleukin (IL)-1β, IL-6, IL-10, Interferon-γ (IFNγ), Transforming Growth Factor- β (TGFβ), and Nuclear Factor-kappa B (NF-κB) were measured using ELISAs. TNFα and TGFβ levels increased while IL-6 and IL-10 levels fluctuated in MCF-7 cells. In conclusion, our study suggests that TCAE may change the normal cancer physiology and lead to cell death by activating apoptosis in MCF-7 cells.