A new family of organometallic p-cymene ruthenium(II) and osmium(II) complexes conjugated to ethacrynic acid, a glutathione transferase (GST) inhibitor, is reported. The ethacrynic acid moiety (either one or two) is tethered to the arene ruthenium(II) and osmium(II) fragments via strongly coordinating modified bipyridine ligands. The solid-state structure of one of the complexes, i.e. [Os(eta(6)-p-cymene)CI][(4'-methyl-[2,2'-bipyridin]-4-y1)methyl-2-(2,3-dichloro-4-(2-methylenebutanoyl)phenoxy)acetate]Cl, was established by single-crystal X-ray diffraction, corroborating the expected structure. The complexes are efficient inhibitors of GST P1-1, an enzyme expressed in cancer cells and implicated in drug resistance, and are cytotoxic to the GST-overexpressing chemoresistant A2780cisR ovarian cancer cell line.