Animal and epidemiologic studies suggest that the use of warfarin might reduce cancer incidence. The antitumor potential of warfarin is demonstrated in different experimental cancer models. Specifically, studies in murine cancer models have shown that warfarin blocks AXL receptor tyrosine kinase by inhibiting a vitamin K-dependent protein called GAS6, thereby may halt the spread of cancer cells. An off-target effect of the anticoagulant warfarin is inhibition of GAS6-AXL signaling, which enhances antitumor immunity and blocks tumorigenesis independently of anticoagulation. Hence, the observed association between warfarin use and lower cancer incidence is likely due to an enhanced antitumor immune surveillance of early cancer. The large observational study also showed a reduction in cancer incidence among regular warfarin users. The study data indicate that warfarin provides a possible cancer protection. Despite some limitations, the results of this study give further support for the hypothesis that warfarin use decreases cancer incidence, which warrants continued investigation. This finding may have important implications for choosing medications in patients who need anticoagulant therapy.