In the article titled “Umbilical Cord Tissue-Derived Mesenchymal Stem Cells Induce T Lymphocyte Apoptosis and Cell Cycle Arrest by Expression of Indoleamine 2, 3-Dioxygenase” [1], the authors identified that the incorrect image was presented in Figure 6(a). The images of T + PHA group in Figure 6(a) and Figure 1(c) were repeated. The authors apologize for this error and explained that the error occurred during manuscript preparation and confirm that it does not affect the results and the conclusions of the article. The corrected Figure 6(a) is as follows: