This study was designed to evaluate the distribution of Tregs/Th17/Th1 cells in type 2 diabetic patients with foot disease before and after human umbilical cord blood mesenchymal stem cell (hUCB-MSCs) transplantation. Fifteen diabetic patients with foot disease under insulin therapy received hUCB-MSC transplantation. The hUCB-MSCs were directly injected into the quadriceps thigh muscles in patients with foot disease (cell quantity at 2 x 10⁶ per point). Physical attributes, blood cytokines, blood glucose and insulin dosage were evaluated before treatment and 1, 2, 4, 8, and 12 weeks thereafter. The ratios of Treg/Th17, Treg/Th1, and Th17/Th1 cells were measured using flow cytometry and their correlation with various cytokines (FoxP3, IL-17, INF-γ, C-RP, TNF-α, and VEGF) was scrutinized. Levels of blood glucose and insulin dosage were significantly reduced in all 15 patients following hUCB-MSC transplantation. The ratios of CD4⁺CD25(hi)FoxP3⁺ Treg/Th17 and CD4⁺CD25(hi)FoxP3⁺ Treg/Th1 cells were significantly increased 4 weeks after transplantation (p < 0.01), while the ratio of Th17/Th1 cells remained unchanged. Serum levels of VEGF peaked at 4 weeks following transplantation. Levels of C-RP and TNF-α were significantly reduced 4 weeks after transplantation. Intriguingly, the ratios of Treg/Th17 were positively correlated with VEGF levels, and were inversely correlated with plasma IL-6 levels. Our data indicated that immune disorders are associated with the development of type 2 diabetes and its complications. Levels of blood glucose and required insulin dosage were reduced after hUCB-MSC transplantation accompanied with improved clinical profiles in diabetic patients. These data favor a role for Treg cells in the onset and progression of T2D.