Objective: To investigate the expression of adrenergic receptors in breast cancer cells and changes in breast cancer cell proliferation after their blockage. Methods: The expressions of adrenergic α1-, α2-, β1- and β2-receptor in breast cancer MCF-7 (ER-positive) and MDA-MB-231 (ER-negative) cells were examined by immunocytochemical staining. The proliferation of the two types of breast cancer cells was analyzed by MTT assay after they were exposed to norepinephrine and carvedilol (non-selective blocker of adrenergic receptors) alone, or in combination, respectively. Results: The MCF-7 and MDA-MB-231 cells both expressed the adrenergic α- and β-receptor, but the expression levels of the adrenergic-receptor subgroups were different between them. The α1- and β1-receptor showed a relatively strong expression while α2- and β2-receptor showed a relatively weak expression in MCF-7 cells, but there was an opposite pattern of expression in MDA-MB-231 cells. The proliferation of both types of breast cancer cells was significantly inhibited by carvedilol treatment, with a certain time- and concentration dependent trend toward higher inhibition, and some of the differences had statistical significance (all P<0.05); the proliferation of both types of breast cancer cells were significantly increased after norepinephrine treatment, which was concentration-dependently antagonized by carvedilol co-treatment, and all the differences reached statistical significance (all P<0.05). Conclusion: Both adrenergic α- and β-receptor are present in breast cancer cells with varying levels of expression, and non-selective blockage of adrenergic receptors can effectively suppress the proliferation of breast cancer cells.