MAIT cells are unconventional T cells expressing a semi-invariant αβ TCR, and they recognize bacterial metabolites via the highly conserved MR1 protein. MAIT cells interact with gut microbiota and literature reports alterations of gut homeostasis in type 1 diabetes (T1D), suggesting the involvement of MAIT cells in T1D. Since NOD mice is a well-established mouse model of T1D, MAIT cells were studied in these mice to evaluate their potential involvement in disease development. This chapter describes the material and methods required to characterize MAIT cells and to determine their function in T1D mouse models.