Abstract Exosomes are 50-100 nm diameter small membrane vesicles secreted from a variety of cells. Although exosomes express a common set of proteins, their protein composition is quite unique and varied significantly. Therefore, their function seems to be dynamic and determined by cell type specific proteins. Human neural stem cells (hNSCs) have been reported to have a therapeutic potential for neuro-regeneration in neurodegenerative disorders. However, the underlying mechanisms of neuroprotective effects of hNSCs are not still clear. In this study, we demonstrated that culture supernatant of hNSC, HB1.F3, can suppress the activation and proliferation of human T cells by apoptosis and cell cycle arrest. More interestingly, we found that exosomes secreted by hNSCs and included in culture supernatant play a critical role in the suppression of T cells by inducing G0/G1 arrest. Therefore, we here suggest that hNSCs has an immunomodulatory effect on T cells without cell-to-cell contact and a possible mechanism is mediated by secreted exosomes.