The resistance of cancer cells to therapy is responsible for the death of most cancer patients. Epithelial-to-mesenchymal transition (EMT) has been associated with resistance to therapy in different cancer cells. However, the mechanisms by which EMT mediates resistance to therapy remain poorly understood. Here, using a mouse model of skin squamous cell carcinoma (SCC) undergoing spontaneous EMT during tumorigenesis, we found that EMT tumor cells were highly resistant to a wide range of anti-cancer therapy both in-vivo and in-vitro. Using gain and loss of function in vitro and in vivo, we uncovered that RhoJ, a small GTPase preferentially expressed in EMT cancer cells, controls resistance to therapy. Using genome-wide transcriptomic and proteomic profiling, we found that RhoJ regulates EMT associated resistance to chemotherapy by promoting DNA damage response and the formation of new replication forks allowing tumor cells to repair DNA lesions more rapidly and survive under the replicative stress induced by chemotherapy. Using affinity-purification followed by mass spectrometry, we found that RhoJ interacts with proteins regulating nuclear actin and the inhibition of actin polymerization sensitizes EMT tumor cells to chemotherapy induced cell death in a Rhoj dependent manner. Altogether, our study uncovers the role and the mechanisms by which RhoJ acts as a key regulator of EMT associated resistance to chemotherapy.