A loose whisker-like Co(OH)2 was synthesized by means of polyethylene glycol 4000 as soft template under ultrasonic condition, and investigated as an active electrode material for electrochemical capacitors. The composition and microstructure of the as-prepared Co(OH)2 were investigated by X-ray diffraction spectroscopy and transmission electron microscopy. The formation mechanism of the whisker-like Co(OH)2 was attentively proposed based on Fourier transform infrared spectroscopy analysis. Electrochemical studies revealed that the whisker-like Co(OH)2 delivered a specific capacitance of 325F/g at a current density of 20mA/cm2 (ca. 1.3A/g) and even 279F/g at 80mA/cm2 (ca. 5.3A/g) due to its special nanostructure, indicating its fast electrochemical response property. A capacitance attenuation of ca. 7% over 1000 cycles meant the good cyclic stability of the whisker-like Co(OH)2 for electrochemical capacitors application.