Well-dispersed spherical nickel powders with uniform size were synthesized via a mild solvothermal route in which aqueous hydrazine was used as reducing agent without any alkaline reagent or surfactant introduced. The as-prepared products were characterized by XRD, FESEM, XPS, and TG. Different influencing factors including solvent, concentration, reaction time, and temperature on the morphology and size of the final products were examined. The size of the spherical nickel powders is tunable from 150 to 800 nm. The obtained nickel powders have little Ni(OH)(2) on the surface and exhibit excellent oxidation resistance. In addition, the formation process was discussed on the basis of the experimental results.