Angiogenesis is a process that forms new blood capillaries from existing vessels, which is of great physiological and pathological significance. Although recent studies provide evidence that cuprous oxide nanoparticles (CO-NPs) may have biomedical potential, the mechanisms of CO-NPs in angiogenesis have not been investigated to date. We have studied the anti-angiogenic properties of CO-NPs on primary human umbilical vein endothelial cells (HUVECs). We found that CO-NPs were able to induce cell morphology changes and suppress cell proliferation, migration and tube formation in vitro and in vivo dose dependently. Furthermore, CO-NPs could induce cell apoptosis both at the early and late apoptotic stage and induce cell cycle arrest at S phase in a dose dependent manner. As signalling via the vascular endothelial growth factor receptor-2 (VEGFR2) is critical for angiogenic responses, we further explored the expression of VEGFR2 after the treatment of CO-NPs. They were found to inhibit VEGFR2 expression dose and time dependently both at the protein and mRNA level while had no effect on VEGF and VEGFR1 expression. Together, we report for the first time that CO-NPs can act as an anti-angiogenic agent by suppressing VEGFR2 expression, which may be a potential nanomedicine for angiogenesis therapy.