Ni nanopowders were sintered by a field-assisted sintering technique (FAST). The influence of heating rate from 90 to 1100 ◦C/min on densification and final grain structure of sintered Ni was studied. A moderate heating rate was found to be beneficial for the densification of Ni nanopowders, whereas a high heating rate was conducive to a lower final density. Very high heating rates resulted in non-uniform densification of the samples and formation of cracks during sintering. Electric field activation and possible densification mechanisms are discussed.