Although it is widely believed that non-segmental vitiligo (NSV) results from the autoimmune destruction of melanocytes, a clear understanding of defects in immune tolerance, which mediate this uncontrolled self-reactivity, is still lacking. In the present study, we systemically evaluated circulating regulatory T (Treg) cells, including CD4+CD25+FoxP3+ Treg cells and invariant natural killer T (iNKT) cells, as well as naïve and memory CD4+ and CD8+ T cells and their cytokine production, in a cohort of 43 progressive NSV patients with race-, gender-, and age-matched healthy controls. We found that the general immunophenotypes of CD4+ and CD8+ T cells and the percentage of CD4+CD25+FoxP3+ Tregs were comparable between NSV and healthy controls. However, percentages of peripheral iNKT cells were significantly decreased in NSV patients compared to that in healthy controls. Our data confirm the previous notion that the percentage of peripheral CD4+CD25+FoxP3+ Tregs remains unaltered in NSV and suggests the involvement of defective iNKT cells in the pathogenesis of NSV.