Synthesis of c-axis grown β-Ni(OH)₂ was attempted by rapid hydrolysis and/or direct hydrothermal treatment of the mixed solution of NiCl₂, HCl and NH₃. The UV–vis spectra revealed the addition of NH₃ into NiCl₂ solution shifted the peak position to shorter wavelength, indicating the formation of nickel ammine complex. Hydrolysis of the mixed solution containing nickel ammine complex gave β-Ni(OH)₂ particles. The amount of NH₃ in the mixed solution did not affect the crystallinity or morphology of the β-Ni(OH)₂ particle by the conventional rapid hydrolysis. Hydrothermal treatment of the hydrolyzed β-Ni(OH)₂ particles was changed the morphology from agglomerated particles to nanosheets-linked structure or hexagonal plates. However, any crystal growth or particular-axis growth was not recognized. Then, the direct hydrothermal treatment of the mixed solution was attempted. The direct treatment at certain amount of coexisting NH₃ gave small amount of the precipitates, and the precipitates showed distinctive XRD pattern of c-axis grown β-Ni(OH)₂. The electrochemical property of the c-axis grown β-Ni(OH)₂ structures indicated that the diffusion control was the rate-determining step for the charge/discharge process.