SLIT-2 is considered as a candidate tumor suppressor gene (TSG) since it is frequently inactivated in various cancers due to hypermethylation of its promoter region and allelic loss. However, the exact mechanism of its tumor suppressive effect has not been elucidated. Here, we observed that Slit-2-overexpressing breast cancer cells exhibited decreased proliferation and migration capabilities compared to control cells under in-vitro conditions. These results were confirmed in-vivo in mouse model systems. Mice injected with MCF-7/Slit-2 cells showed a 60-70% reduction in tumor size compared to mice injected with MCF-7/VC cells both in the absence and presence of estrogen. Upon further elucidation, we observed that Slit-2 mediates the tumor suppressive effect via a coordinated regulation of the beta-catenin and PI3-kinase signaling pathways and by enhancing beta-catenin/E-cadherin-mediated cell-cell adhesion. Our study for the first time reveals that Slit-2-overexpressing breast cancer cells exhibit tumor suppressor capabilities through the novel mechanism of beta-catenin modulation.