The bulk specific heat of fully dense nanocrystalline Ni-P electrodeposits with essentially constant P content (about 4 at%) and varying average grain sizes from 6.9 to 28.9 nm was investigated using modulated differential scanning calorimetry. In the lower temperature range from room temperature to 120 A degrees C, at which the as-deposited sample microstructure was thermally stable, the bulk specific heat varied only within similar to 2 % despite the substantial variation of interface volume fractions from 0.11 to 0.39 for this series of samples. Moreover, the measured bulk specific heat values of the Ni-P samples were all located within the reported specific heat value range for conventional polycrystalline Ni. Evidently, the contribution due to grain size-related interface excess free volume is negligible and the bulk specific heat for the materials can be characterized as a structure-insensitive property. In the elevated temperature range from 150 A degrees C to the Curie temperature of 357 A degrees C, the magnetic contribution to the specific heat was significantly influenced by the chemical environment of P in the Ni-P samples. When P atoms were in the form of supersaturated solution in the nickel matrix, a complete suppression of the characteristic lambda peak of the magnetic contribution in the specific heat curves was observed for all materials. The lambda peak re-appeared in the specific heat curve after the Ni-P sample underwent a transformation to a two-phase microstructure consisting of Ni and Ni3P grains. It can be concluded that at a given P content, paramagnetic phosphorus atoms in the form of solutes are more effective in reducing the magnetic contributions to the specific heat than the form of paramagnetic Ni3P second-phase particles for the nanocrystalline Ni-P alloy.