Porous nickel oxide (NiO) nanofibers, structured with and composed of linearly oriented NiO nanoparticles, were synthesized via a simple method using a solution containing ethanol, H2O, NiCl2, and P123 (Pluronic P123, a triblock copolymer H(OCH2CH2)(20)(OCH(CH3)CH2)(70)(OCH2)(20)OH). By adjusting the concentration of P123, this method allows for the control of the fiber morphology and the nanoparticle size.