Invariant NKT cells (iNKT) represent a unique subset of innate lymphocytes that play a dual role and exert a pro-inflammatory function and also a tolerogenic function that is crucial to maintain T cell tolerance and prevent autoimmune diseases like Multiple Sclerosis, Type 1 Diabetes, Rheumatoid Arhritis and Systemic Lupus Erithematosus (SLE). Although a large body of evidence indicated that iNKT cells are instrumental to counter-regulate T cell-mediated autoimmune diseases, there is still some controversy on whether iNKT cells can actively induce immunosuppression and directly dampen T cell autoimmunity. Moreover, the recent discovery of a distinct iNKT cell subset, the iNKT17 cells, with strong adjuvant and pro-inflammatory function raised the question on what is the role of NKT17 cells in the pathogenesis of autoimmune diseases. Here, we review the current knowledge on iNKT cell biology and focus our attention on the possible mechanism of action and final effect of the different iNKT cell subsets in the pathogenesis of T cell-mediated autoimmune diseases.