Hydrolysis of carboxylic estersp-nitrophenyl acetate (pNPA), p-nitrophenyl butyrate (pNPB) and p-nitrophenyl trimethyl acetate (pNPTA) was examined in oxovanadate solutions by means of ¹H and ⁵¹V NMR spectroscopy. In the presence of a mixture of oxovanadates, the hydrolysis of carboxyester bonds in pNPA proceeds under physiological conditions (37 °C, pD = 7.4) with a rate constant of k_obs = 3.0 × 10⁻⁵ s⁻¹ representing an acceleration of at least one order of magnitude compared to the uncatalyzed cleavage. EPR and NMR spectra did not show evidence for the formation of paramagnetic species, excluding the possibility of V(+5) reduction to V(+4), and indicating that the cleavage of the carboxyester bond is purely hydrolytic. The pH dependence of k_obs revealed that the hydrolysis is slow in acidic media but rapidly accelerates in basic solutions. Comparison of the rate profile with the concentration profile of polyoxovanadates shows a clear overlap of the k_obs profile with the concentration of monovanadate (V₁). Kinetic experiments at 37 °C using a fixed amount of pNPA and increasing amounts of V₁ permitted the calculation of catalytic (k_c = 1 x10⁻⁴ s⁻¹) and formation constant for the pNPA–V₁ complex (K_f = 17.5 M⁻¹). The ⁵¹V NMR spectra of a reaction mixture revealed broadening and shifting of the ⁵¹V NMR resonances of the V₁ and V₂ upon addition of increasing amount of pNPA, suggesting a dynamic exchange process between vanadates and pNPA, occurring via a rapid association–dissociation equilibrium. The origin of the hydrolytic activity of vanadate is most likely a combination of its nucleophilic nature and the chelating properties which can lead to the stabilization of the transition state.