Halogenido and carboxylato Ru(II) half-sandwich complexes of the general composition [Ru(η6-p-cym)(dpa)X]PF6 (1–5) were prepared and thoroughly characterized with various techniques (e.g., mass spectrometry, NMR spectroscopy and X-ray analysis); dpa = 2,2′-dipyridylamine; p-cym = p-cymene; X = Cl− (for 1), Br− (for 2), I− (for 3), valproate(1−) (for 4) or 4-phenylbutyrate(1−) (for 5). A single-crystal X-ray analysis showed a pseudo-octahedral piano-stool geometry of [Ru(η6-p-cym)(dpa)I]PF6 (3), with a η6-coordinated p-cymene, bidentate N-donor dpa ligand and iodido ligand coordinated to the Ru(II) atom. The results of the 1H-NMR solution behaviour studies proved that the complexes 1–5 hydrolyse were in the mixture of solvents used (10% MeOD-d4/90% D2O). Complexes 1–5 were in vitro inactive against the A2780 human ovarian carcinoma cell line, up to the highest tested concentration (IC50 > 100 μM).