Src kinase plays a key role in multiple signalling pathways regulating diverse cell functions from proliferation and survival to invasion and angiogenesis. In breast cancer, both Src protein levels and kinase activity are frequently elevated and its important role in these oncogenic processes make it a potential target for therapeutic intervention. Importantly, recent evidence has revealed a role for Src in mediating anti-hormone action and in acquired endocrine resistance. A number of small molecule inhibitors of Src kinase have been developed with preclinical data demonstrating their effectiveness at suppressing breast cancer growth and invasion in vitro whilst inhibiting disease spread in vivo. Significantly, there appears to be added benefit when these agents are given in combination with anti-oestrogens. These new findings suggest that Src inhibitors might have therapeutic value in breast cancer patients.