In this study, we developed a complementary electrochromic device consisting of MoO3 and NiO films fabricated by electron beam evaporation, and lamination, with an ethyl cellulose-based gel polymer electrolyte. The device comprises a MoO3 film as the main cathodic electrochromic layer, a gel polymer electrolyte as an ion conduction layer, and a NiO film as the complementary, anodic electrochromic layer. After investigating the properties of MoO3 film, NiO film, and complementary electrochromic devices, we concluded that this device provides good reversibility, low power consumption of -1.5 V in color state, high variation of transmittance of 51.9%, changes in optical density of 0.754, coloration efficiency of 54.9 cm(2)/C and good memory effect under open-circuit conditions. Our results demonstrate that ethyl cellulose-based gel polymer electrolyte is electrochemically stable, and overcomes leakage problems generally associated with such electrolytes. It may be used as an ion-conducting medium for complementary electrochromic devices, and as such, exhibits excellent electrochromic characteristics. (C) 2012 Elsevier B.V. All rights reserved.