Time-resolved fluorescence-upconversion spectroscopy has been used to study the polar solvation dynamics of H2O and D2O at the surface of zirconia (ZrO2) nanoparticles. While an isotope effect is observed for the solvation dynamics of. bulk D2O, there is no isotope effect on the interfacial solvation dynamics. The interfacial solvation dynamics are the same for H2O and D2O and are faster than the bulk solutions. The bulk isotope effect is due to stronger hydrogen bonding in D2O compared to H2O, slowing the reorientation of the excited-state dipoles in the bulk D2O. The lack of isotope effect for the interfacial dynamics is explained in terms of the solvent interacting with the ZrO2 surface.