Infusion of Wharton’s jelly-derived MSCs to NOD mice at the onset of diabetes led to normal glucose homeostasis within 6–8 days that lasted for 6 weeks.Infusion of Wharton’s jelly-derived MSCs to NOD mice prior to onset of diabetes resulted in an 8-week delay in the onset of diabetes.The MSC infusion resulted in higher fasting C-peptide levels, higher frequencies of CD4+CD25+Foxp3+ regulatory T lymphocytes, and lower levels of IL-2, IFNγ, and TNFα. Here, FOXP3 is linked to diabetes mellitus.