We report the synthesis of sphere-like α-Ni(OH)(2) nanoarchitecture by self-assembly with the aid of hexamethylenetetramine (HMT). The α-Ni(OH)(2) nanoarchitectures, with a diameter of several micrometres, are composed of many nanoflakelets about 10 nm in thickness. The influences of the reaction temperature, time, reagent, nickel salt and pH value on the morphology and structure of the α-Ni(OH)(2) were studied, the chemical and thermal stability are discussed, and the formation mechanism is proposed. The α-Ni(OH)(2) nanoarchitectures display a good electrochemical capacity.