We report on in situ heat capacity measurements (370-800 K) using quasiadiabatic ultrafast differential scanning nanocalorimetry in thin films (1-200 nm) of Ni grown by electron beam evaporation. The heat capacity shows a broad peak with a rounded maximum that is attributed to the decrease of long-range interactions in the ferromagnetic to paramagnetic phase transition of Ni. The calorimetric data exhibit a reduction of the Curie temperature as the thickness of the films (or the average grain size) decreases. The magnitude of the jump in specific heat at TC scales with the number of surface or interface atoms. © 2008 American Institute of Physics.