Communication: All-plastic and flexible electrochromic devices will facilitate new technological applications, such as information display and storage, in the automotive industry (rear-view mirrors) and in architecture (smart windows). Here the authors describe an all-plastic and flexible solid-state electrochromic device using two optically complementary conductive polymer blends deposited on ITO-PET (indium tin oxide-poly(ethyleneterephthalate)), and a polymeric electrolyte. The device was constructed under atmospheric conditions and showed good optical characteristics.