Bone morphogenetic proteins (BMPs) are involved in diverse biological processes, including cell proliferation, differentiation and apoptosis. Results from the MTT assay revealed that BMP-2 significantly inhibited the proliferation of MDA-MB‑231 and MCF-7 breast cancer cells. The flow cytometric analysis demonstrated that BMP-2 caused G1 arrest and promoted apoptosis. An increase in p21 and cleaved caspase-3 in the two cell lines was detected by western blot analysis, which may be responsible for the suppression of cancer cell proliferation caused by BMP-2. BMP-2 protected MDA-MB-231 and MCF-7 cells from generating xenograft tumors in nude mice. Thus, BMP-2 may be considered as an inhibitor of breast cancer at the early stages of disease.