Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) measurements were performed on an electroless plated Ni-P amorphous alloy to study the influence of different heat-treatments (linear heating and isothermal annealing). The phases formed after crystallization and the average grain size of the crystallization products were determined from XRD line broadening, and the heat evolved during the structural transformations were established from DSC measurements. A detailed study of the transformation products obtained along different heating routes was performed. From these studies, a scheme of the structural transformations and their energetics was constructed. The grain boundary energies in the different nanocrystalline states were also estimated.