The reactions of Na₂PtCl₄ with pyridine-2-carbaldehyde and 2-acetyl pyridine N(4)-ethyl-thiosemicarbazones, HFo4Et and HAc4Et respectively, afforded the complexes [Pt(Fo4Et)Cl], [Pt(HFo4Et)₂]Cl₂, [Pt(Fo4Et)₂] and [Pt(Ac4Et)Cl], [Pt(HAc4Et)₂]Cl₂·2H₂O, [Pt(Ac4Et)₂]. The new complexes have been characterized by elemental analyses and spectroscopic studies. The crystal structure of the complex [Pt(Ac4Et)Cl] has been solved. The anion of Ac4E coordinates in a planar conformation to the central platinum(II) through the pyridyl N, azomethine N and thiolato S atoms. Intermolecular hydrogen, non-hydrogen bonds, π–π and weak Pt–π contacts lead to aggregation and a supramolecular assembly. The cytotoxic activity for the platinum(II) complexes in comparison to that of cisplatin and thiosemicarbazones was evaluated in a pair of cisplatin-sensitive and -resistant ovarian cancer cell lines A2780 and A2780/Cp8. The platinum(II) complexes showed a cytotoxic potency in a very low micromolar range and were found able to overcome the cisplatin resistance of A2780/Cp8 cells.