Glioma initiating cells (GICs), which reside within the perivascular microenvironment to maintain self-renewal capacity, are responsible for glioblastoma initiation, progression, and recurrence. However, the molecular mechanisms controlling crosstalk between GICs and endothelial cells are poorly understood. Here we report that, in both GICs and endothelial cells, platelet derived growth factor (PDGF)-driven activation of nitric oxide (NO) synthase increases NO-dependent inhibitor of differentiation 4 (ID4) expression, which in turn promotes JAGGED1-NOTCH activity through suppression of miR-129 that specifically represses JAGGED1suppression. This signaling axis promotes tumor progression along with increased GIC self-renewal and growth of tumor vasculature in the xenograft tumors, which is dramatically suppressed by NOTCH inhibitor. ID4 levels correlate positively with NOS2, HES1, and HEY1 and negatively with miR-129 in primary GICs. Thus, targeting the PDGF-NOS-ID4-miR-129 axis and NOTCH activity in the perivascular microenvironment might serve as an efficacious therapeutic modality for glioblastoma.