Platinum(II) complexes having mixed ligands as anticancer agents. The central platinum atom is coordinated by two phosphine ligands and two heterocyclic thione ligands. Each heterocyclic thione ligand has a five-, six- or seven-membered heterocyclic ring with two nitrogen atoms at positions 1 and 3 of the ring and a thiocarbonyl group at position 2. Pharmaceutical compositions incorporated the platinum(II) complexes, methods of synthesizing the complexes and methods of treating cancers with the complexes or pharmaceutical compositions thereof are also described.