Natural killer T (NKT) cells are a subset of regulatory T lymphocytes that recognize glycolipid antigens presented by the major histocompatibility complex class I-related glycoprotein CD1d. NKT cells have been implicated in regulating the progression of Type 1 diabetes (T1D) in human patients and in an animal model for T1D. In addition, glycolipid agonists of NKT cells have been successful in preventing diabetes in mice, raising enthusiasm for the development of NKT cell-based therapies for T1D.