A core–shell composite of porous ZnO nanosheets and a multichromic conducting polymer poly(4,4′,4′′-tris[4-(2-bithienyl)pheny]amine) (PTBTPA) was prepared by electrodeposition combined with the electropolymerization method. The composite film exhibits noticeable electrochromism with reversible color changes from orange, olive green to dark gray. An optical contrast of 68.7% and a switching time of 0.96 s are obtained for the composite film, better than that of the pure PTBTPA film, 51.8% and 1.95 s. The cyclic stability studies reveal that the composite film exhibits much more enhanced durability and retains 70% of the electroactivity even after 1000 cycles. However, the pure PTBTPA film loses almost most of its electroactivity after 1000 cycles. The core–shell composite structure is believed to be responsible for the observed enhanced electrochromic performance. On one hand, porous ZnO nanosheets with loose inner space can facilitate the penetration of counterions into the polymer film and shorten the diffusion distance, resulting in the higher optical contrast and faster switching speed; on the other hand, the larger contact area can enhance the adhesion between the polymer and the ITO electrode, contributing to better electrochemical stability.