Flavonoid compounds have been shown to trigger cell cycle arrest at G0/G1, S and G2/M checkpoints, allowing cells to repair DNA damage before entry into mitosis. Jaceosidin, a flavonoid compound, has been reported to induce apoptosis in various cancer cell lines. In our previous study, we established that jaceosidin induces apoptosis in U87 glioblastoma cells through G2/M phase arrest. However the molecular mechanisms oremained unclear. In the present study, mRNA and protein expression levels of major cell cycle regulatory genes were analyzed by semi-quantitative RT-PCR and Western blot studies respectively. The results demonstrated that jaceosidin-induced G2/M phase arrest in U87 cells is associated with DNA fragmentation, up-regulation of p53 and p21 and subsequent down-regulation of cyclin B1 and CDK1 expression at mRNA as well as at protein level. These findings provide insights into jaceosidin-induced G2/M phase arrest in U87 glioblastoma cells.