A metal complex nanosheet was synthesized by the liquid-liquid interface self-assembly method from a star-shaped ligand of tris[4-(4'-2,2':6',2''-terpyridyl)-phenyl]amine in organic solvents and metal ion Fe(ii) in water solution. The as-prepared nanosheet possessed excessively smooth morphology with a thickness of hundreds of nanometers. Adhering to an ITO glass, the nanosheet showed noticeable electrochromism from purplish red at 0 V to orange-yellow at 1.4 V and green at 1.6 V. Besides, the nanosheet exhibited outstanding stability with the optical contrast maintained at almost 100% of its original electrochemical activity over 500 cycles. The liquid-liquid interface self-assembly method was proven to be promising to prepare a polymeric metal complex for potential electrochromic applications.