Here, we report a natural chemical Matrine, which exhibits anti-melanoma potential with its PTEN activation mechanism. Matrine effectively inhibited proliferation of several carcinoma cell lines, including melanoma (V600E)BRAF harboring M21 cells. Flow cytometry analysis showed Matrine induced G(0)/G(1) cell cycle arrest in M21 cells dose-dependently. Apoptosis in M21 cells induced by Matrine was identified by Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) analysis and Annexin-V/FITC staining. Molecular mechanistic study suggested that Matrine upregulated both mRNA level and protein expression level of phosphatase and tensin homolog deleted on chromosome ten (PTEN), leading to inhibition of the PI3K/Akt pathway. Downregulation of phosphor-Akt(ser473) by Matrine activated p21 and Bax, which contributed to G(0)/G(1) cell cycle and apoptosis. Besides, Matrine enhanced the PI3K/Akt inhibition effects to inhibit the cell proliferation with PI3K inhibitor, LY2940002. In summary, our findings suggest Matrine is a promising antitumor drug candidate with its possible PTEN activation mechanisms for treating cancer diseases, such as melanomas.