The malignant phenotype of glioblastoma multiforme (GBM) is believed to be largely driven by glioma stem-like cells (GSCs), and targeting GSCs is now considered a promising new approach to treatment of this devastating disease. Here, we show that SN50, a cell-permeable peptide inhibitor of NFκB, induced robust differentiation of human GSCs, causing loss of their oncogenic potential. We observed that following treatment of GSCs with SN50, their differentiated progeny cells showed significant decreases in their capability to form neuro-spheres and to invade in vitro and a reduction in their tumorigenicity in mouse xenograft models, but had increased sensitivity to the chemotherapeutic drug temozolomide and to radiation treatment. These results suggest that blocking the NFκB pathway may be explored as a useful mean to induce differentiation of GSCs, and provide another supportive evidence for the promise of differentiation therapy in treatment of malignant brain tumors.