The effect of NaCl concentration on the redox potential of alpha-ferrocenylundecyl-omega-hydroxy-polyoxyethylene (FPEG) micelles has been studied in aqueous solutions. With increasing NaCl concentration, the anodic half-wave potentials E-1/2 of cyclic voltammograms of the aqueous solutions shift to higher potential, and the peak currents of the cyclic voltammograms decrease. The results are discussed in terms of thermodynamics of the micelle formation. An equation which interprets the correlation between the E-1/2, the salt concentration, diffusion coefficient of the micelle D-M, and the aggregation number m, has been derived. The changes in D-M and m with NaCl concentration do not explain the change in the value of E-1/2. The decrease in the equilibrium constant for the micelle-disruption K-d with increasing NaCl concentration affects the redox-potential of the FPEG micellar solutions.