Background: The mammalian target of rapamycin (mTOR) is important in hematopoiesis. Despite the central role of mTOR in regulating the differentiation of immune cells, the effect of mTOR function on cord blood mononuclear cells is yet to be defined. Objectives: To evaluate the effect of mTOR inhibition, using rapamycin on the proliferation and apoptosis of cord blood mononuclear cells, as well as on the B and T cell expansion. Methods: Cord blood mononuclear cells were cultured in the presence of IL-2, IL-7 and IL-15 cytokines and inhibited by rapamycin for 14 days. The harvested cells were evaluated at distinct time points by flow cytometry. Results: The mTOR expression decreased in the presence of rapamycin on day 14. Inhibition of mTOR reduced the proliferation of the cord blood mononuclear cells, yet did not influence apoptosis. Moreover, the number of T and NK cells was significantly reduced in the presence of rapamycin, while no change was observed in the B cell expansion. Conclusion: mTOR signaling plays a crucial part in cord blood derived NK and T cells expansion.