Doxorubicin (Dox) is a commonly used chemotherapeutic drug in human colon cancer. However, it becomes increasingly ineffective with tumor progression, the underlying mechanism of which remains to be elucidated. Emerging evidence has led to the identification of an association between chemoresistance and the acquisition of epithelial-mesenchymal transition (EMT) in cancer. However, it remains to be elucidated whether this process is involved in the development of resistance to Dox in colon cancer. In HCT116 human colon cancer cells treated with Dox (50 nmol/l), EMT was induced, and transforming growth factor (TGF)β signaling and multi-drug resistant plasma membrane glycoprotein levels were significantly increased. By contrast, silencing of Smad4, using stable RNA interference, inhibited TGFβ signaling, reversed the process of EMT and markedly increased the sensitivity of HCT116 cells to Dox. The results of the present study suggested that the combination of Dox with the downregulation of TGFβ signaling may be a potential novel therapeutic strategy with which to overcome chemoresistance during colon cancer chemotherapy.