The complex [Ru(η2-O2CCH2CH3)(dppe)2]PF6 (dppe=1,2-bis(diphenylphosphino)ethane) was prepared and characterized by elemental analysis, spectroscopic techniques, X-ray crystallography, HRESIMS and HRESIMS/MS. The characterization data are consistent with a cis arrangement for the dppe ligands and a bidentate coordination of the propionate ligand through carboxylate oxygens. Cytotoxicity assays were carried out on human and murine cancer and normal cell lines. In general, the [Ru(η2-O2CCH2CH3)(dppe)2]PF6 complex was more cytotoxic than both its precursor cis-[RuCl2(dppe)2] and the reference metallodrug cisplatin. The best results against the HepG2 human tumour cell line and S180 murine tumour cell line were found with IC50 values of 6.5±0.2 and 0.18±0.03μM, respectively.