Novel ruthenium half-sandwich complexes containing (N,O)-bound pyrazolone-based β-ketoamine ligands have been prepared, and the solid-state structures of one ligand and five complexes have been determined by singlecrystal X-ray diffraction. Some of the complexes display moderate cytotoxicity toward the human ovarian cancer cell lines A2780 and A2780cisR, the latter line having acquired resistance to cisplatin.