AbstractNovel hybrid nanocomposites based on the immobilisation of tetrabutylammonium salts of phosphomolybdates (PMo12, PMo11, PMo11V, and PMo10V2) on single‐walled carbon nanotubes or graphene flakes were prepared. Glassy carbon electrodes modified with carbon nanocomposites produce cyclic voltammograms that are consistent with surface‐confined redox processes attributed to Mo‐centred reduction (MoVI→MoV) and vanadium reduction (VV→VIV) for PMo11V and PMo10V2. Furthermore, they show very high stabilities and well‐resolved redox peaks with high current intensities. The observed enhancement of the electrochemical properties of polyoxometalates (POMs) is a consequence of strong electronic communication between POMs and carbon nanomaterials. Nanocomposites of vanadium–phosphomolybdates exhibit superior V‐based electrocatalytic properties towards ascorbic acid oxidation in comparison with free POMs; moreover, PMo11V@graphene shows an outstanding sensing performance for the detection of dopamine.