Thymopentin is an immune-modulating peptide that can stimulate cellular immune responses and has been used in many immune handicapped cases [1]. However, despite documented reports proving its efficacy in immunoregulation, there have been no reports, as yet, concerning its impact on the maturation and function of dendritic cells (DCs). In this study, we analyzed the effects of thymopentin on the detailed regulation of maturation of murine bone-marrow-derived DCs (BMDCs). The phenotypic and structural maturation of BMDCs was confirmed by transmission electron microscopy (TEM) and flow cytometry (FCM). The functional maturation was confirmed by an acid phosphatase (ACP) activity test, FITC-dextran bio-assay, test of 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE), labeled CD4(+)T cell proliferation and enzyme-linked immunosorbent assay (ELISA). We determined that thymopentin up-regulated the expression of CD40, CD80, CD86, CD83, and MHC II molecules on BMDCs, down-regulated phagocytosis of BMDCs, increased BMDCs driven CD4(+)T cell proliferation, and enhanced BMDC production of IL-12 and TNF-α. Therefore, we concluded that thymopentin highly induces BMDC maturation and intensifies DC/T-cell pathways. These data also provide direct evidence and rationale concerning the potential clinical use of thymopentin in various immune handicapped cases and suggest that thymopentin should be considered as a potent adjuvant for DC-based vaccines.