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 2x106 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+CD25hiFoxP3+ Treg/Th17 and CD4+CD25hiFoxP3+ 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.