The prognosis of patients diagnosed with glioblastoma remains dismal in spite of the current concomitant chemoradiotherapy with temozolomide. In particular, the resistance to temozolomide appears to be the greatest obstacle to the treatment of glioblastoma. In the present study, we evaluated in vitro and in vivo the antitumor effects of combination therapy of cilengitide with belotecan, a camptothecin derivate, to treat experimental glioblastoma. The therapeutic effects of the drugs on the U87MG and U251MG human glioblastoma cell lines were assessed using in vitro cell viability and apoptosis assays. The combination treatment group with cilengitide and belotecan enhanced the cytotoxic effects to the glioblastoma cell lines and increased the apoptosis of the tumor cells compared to monotherapy with either drug alone in vitro. Nude mice with established U87MG glioblastoma were assigned to the following four groups: control, cilengitide, belotecan and combination treatment. The volume of tumors and length of survival were also measured. Animals in the combination therapy group demonstrated a significant reduction of tumor volume and an increase in survival (p < 0.05). Immunohistochemistry revealed a decrease in angiogenesis by cilengitide and an increase in apoptosis by cilengitide and belotecan in vivo. The combination therapy of cilengitide with belotecan presented more cytotoxic effects compared to the monotherapy of either drug in vitro and in vivo. This combination protocol may serve as an alternative treatment option for glioblastoma.