MS023 is a potent, selective, and cell-active inhibitor of human type PRMTs (protein arginine methyltransferase), which is involved in many biological processes. Overexpression of PRMTs is related to some cancers. Therefore, MS023 is a useful chemical tools for testing biological and therapeutic hypotheses. MS023 displayed high potency for type I PRMTs including PRMT1, -3, -4, -6, and -8 but was completely inactive against type II and type III PRMTs, protein lysine methyltransferases and DNA methyltransferases. MS023 potently decreased cellular levels of histone arginine asymmetric dimethylation. It also reduced global levels of arginine asymmetric dimethylation and concurrently increased levels of arginine monomethylation and symmetric dimethylation in cells.