Recent studies have shown that transforming growth factor-β1 (TGF-β1) signaling plays important roles in the redox system in benign and malignant cells. Whether TGF-β mediates an antioxidative damage response in colorectal cancer cells is largely unknown. Herein, using the human colorectal cancer cell lines we found that TGF-β1 induced glutathione peroxidase-1 (GPx-1) expression and enzyme activity, and that the upregulation of GPx-1 by TGF-β1 could protect colorectal cell lines from H2O2-induced oxidation damage. Further, we used loss- and gain-function approaches to elucidate the underlying mechanism and found that TGF-β1 induced GPx-1 through activation of the TGF-β receptor type I (TGF-βRI)/Smad2/extracellular-signal-regulated kinase 1/2 (ERK1/2)/hypoxia-inducible factor-1α (HIF-1α) signaling pathway. This cascade could be blocked by the TGF-βRI inhibitor or ERK1/2 inhibitor. Taken together, our data demonstrated that TGF-β1 induced GPx-1 expression and enzymatic activity via the TGF-βRI/Smad2/ERK1/2/HIF-1α signaling pathway, suggesting a novel antioxidative protective function of TGF-β1 in colorectal cancer cells.