GRIM-19 (Gene associated with Retinoid-Interferon-induced Mortality 19) is a novel tumor suppressor regulated by interferon/retinoid combination. We have recently shown that GRIM-19 inhibits v-Src-induced oncogenic transformation and metastatic behavior of cells. Oncogenic v-Src induces cell motility by cytoskeletal remodeling, especially the formation of podosomes and. Here, we show that GRIM-19 inhibited the v-Src-induced cell motility by inhibiting cytoskeletal remodeling, that is, podosome formation. We also show that the N terminus of GRIM-19 played a major role in this process and identified critical residues in this region. More importantly, we show that tumor-associated GRIM-19 mutations disrupted its ability to inhibit v-Src-induced cell motility. These actions appear to occur independently of STAT3, a known target of GRIM-19-mediated inhibition. Lastly, tumor-associated GRIM-19 mutants significantly lost their ability to control v-Src-induced metastases in vivo, indicating the biological and pathological significance of these observations.