Histone methylation has been highlighted in the regulation of gene expression. To explore the role of histone methylation in angiogenesis, methylstat, a Jumonji C domain containing the histone demethylase inhibitor, was used as a chemical probe. Methylstat inhibited the cell cycle of human umbilical vascular endothelial cells (HUVECs) at lower concentrations than other cell lines tested. Furthermore, methylstat blocked in vitro and in vivo angiogenesis at a nontoxic dose. These results provide new insights into the role of histone demethylase in angiogenesis. Collectively, methylstat could be a promising chemical probe for addressing its role in angiogenesis.