Up-regulation of integrin alpha(v)beta(3) has been shown to play a key role in tumor angiogenesis and metastasis. In this study, we evaluated the role of integrin alpha(v)beta(3) in breast cancer cell resistance to ionizing irradiation (IR) and tested the anti-tumor efficacy of combining integrin alpha(v) siRNA and IR. Colonogenic survival assay, cell proliferation, apoptosis, and cell cycle analysis were carried out to determine the treatment effect of siRNA, IR, or combination of both on MDA-MB-435 cells (integrin alpha(v)beta(3)-positive). Integrin alpha(v)beta(3)-negative MCF-7 cells exert more radiosensitivity than MDA-MB-435 cells. IR up-regulates integrin alpha(v)beta(3) expression in MDA-MB-435 cells and integrin alpha(v) siRNA can effectively reduce both alpha(v) and alpha(v)beta(3) integrin expression, leading to increased radiosensitivity. Integrin alpha(v) siRNA also promotes IR-induced apoptosis and enhances IR-induced G2/M arrest in cell cycle progression. This study, with further optimization, may provide a simple and highly efficient treatment strategy for breast cancer as well as other integrin alpha(v)beta(3)-positive cancer types.