Nickel nanowires were synthesized via electroless deposition in an organic solvent (ethylene glycol) under a magnetic field. Deposition behavior of nickel particles and wires were electrochemically investigated at various concentrations of NaOH by an in-situ mixed potential measurement and voltammetry combined with quartz crystal microbalance. Based on the electrochemical investigation, a formation mechanism of nickel wires is proposed. According to the mechanism, nickel wires 100-370 nm in diameter with several dozen mu m of length were successfully prepared by controlling the reduction rate by varying a concentration of sodium hydroxide, trisodium citrate, and a nucleating agent, chloroplatinic acid. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3596703] All rights reserved.