Breast cancer is the second most diagnosed type of cancer in the world, although it is more prevalent in women and can affect both women and men. This type of cancer is the fifth leading cause of death. Even though there are multiple treatment protocols, there is a need to develop more effective alternatives. The current study explores the effects on breast cancer cell lines, MCF-7 (metastatic cell line) and MDA-MB-231 (non-metastatic), of pharmaceuticals like β-blockers already prescribed to treat other diseases. Thus, cell lines were exposed, up to 72h, to non-selective β-blockers, propranolol (10-250 μM) and carvedilol (0.1-100 μM), to antimetabolites, methotrexate (0.01-20 μM) and 5-fluorouracil (0.1-50 μM) and cell viability was assessed. The obtained results demonstrated higher sensitivity of MCF-7 to the tested drugs. Based on the estimated medium lethal concentration, carvedilol was the most toxic drug followed by propranolol and cytostatic drugs. Data support the potential application of beta-blockers in the treatment of breast cancer.