Background and Objectives: Hematopoietic stem cells (HSCs) have become a standard protocol for the treatment of many hematologic malignancies and non-malignant disorders. Umbilical cord blood, as a source of HSCs, has many advantages compared to other sources. One major drawback in using this source in transplantation is the low HSC dose available. Ex vivo expansion of HSCs is a solution to overcome this limitation. In this study, we used TEPA, as a Cu chelator, and human bone marrow MSCs to investigate the expansion rate of UCB-HSCs.Materials and Methods: CB-HSCs were isolated using miniMACS magnetic separation system. We cultured the enriched CD34+ cells in various conditions. Culture condition A, supplemented only with recombinant cytokines; culture condition B, supplemented with BM-MSCs as a cell feeder layer and recombinant cytokines; culture condition C, supplemented with recombinant cytokines and TEPA; culture condition D, supplemented with recombinant cytokines, BMMSCs as a cell feeder layer and TEPA. In order to evaluate the HSC expansion, we performed cell count, the analysis of CD34+ expression by flow cytometery, and CFU assay on day 10 after culture.Results: The most fold increase rate in CD34+ cell, TNCs and CFU-C was observed in the culture condition D (110.11±15.3, 118.5±21 and 172.9±44.7, respectively) compared to other conditions.Conclusions: The results showed that co-culture of HSCs with BM-MSCs in the presence of copper chelating agent (TEPA) could dramatically increase the expansion rate of UCB-HSCs.Therefore, this strategy could be useful for HSC expansion.