The title compound, [Cu(C(3)F(5)O(2))(C(3)H(9)OP)(4)](C(3)F(5)O(2)), comprises a cationic Cu(II) complex and a disordered penta-fluoro-propionate counter-ion. The metal atom has a distorted square-pyramidal coordination environment formed by four O atoms originating from trimethyl-phosphine oxide mol-ecules and the remaining one belonging to the monodentate penta-fluoro-propionate anion, which is situated in the basal plane of the pyramid. The mol-ecules are held together in the crystal by a net of weak C-H⋯O and C-H⋯F hydrogen bonds. The counter anion is disordered over two sets of sites in a 0.629 (5):0.371 (5) ratio.