USP9x is a deubiquitylating enzyme that is highly expressed in neural progenitors in the developing murine brain. Increased levels of USP9x enhance neural progenitor self-renewal in vitro. Deletion of Usp9x in vivo affects several neural progenitor functions including proliferation, polarity and adhesion. To determine if USP9x has a direct role in neural progenitor/stem cell proliferation, we depleted USP9x protein using inducible shRNA interference in the immortalised human neural stem cell line, ReNcells VM. Depletion of USP9X rapidly led to a reduction in cellular density, reduced cellular proliferation and an accumulation of cells in the G0/G1 phase. To determine if cells were arresting at the G1-S phase transition, we investigated the status of cell cycle proteins involved at this phase and showed a reduction in phosphorylated retinoblastoma protein, pRbS780, whilst other cell cycle proteins levels remained unchanged. We also showed that after EGF/FGF stimulation there is reduced mTORC1 and mTORC2 activity, as measured by phosph-S6ser235/236 and phosphor-AktSer473, respectively, in USP9x depleted cells. We further demonstrated a reduction of mTORC1 and mTORC2 components: Raptor and Rictor. This suggests that USP9x may stabilise Raptor and Rictor proteins in neural stem cells to promote EGF/FGF signalling through the mTOR cell growth and proliferation cascade.