There is evidence indicating that multilayer films can be harder than monolithic ones. To investigate this, TiN/NbN multilayers with bilayer thicknesses ranging from 4 nm to 30 nm have been grown on MgO (001) single crystals using reactive magnetron sputtering. The sharpness of the interface and the composition modulation, which would be expected to strongly influence dislocation motion, have been studied by X-ray diffraction (XRD). These experiments show that the interfaces remain reasonably sharp (interface thickness ∼1 nm) and the composition modulation amplitude is maximum for multilayers with bilayer thicknesses greater than ∼10 nm. With thinner bilayers, the composition modulation decreases but the layered structure remains. Despite this, the nanoindentation hardness of the multilayers is between 20 and 25 GPa, which is similar to that of TiN and NbN alone, and therefore, no hardening due to the layering is observed. The deformation mechanisms observed under the indent in the TEM are consistent with these results.