In recent years, the fabrication of Janus materials and their potential applications has been of much interest in Materials Science. Here, we report the fabrication of an entirely novel structure–Janus nanowalls and the phenomenon of lateral buckling in them. Polymeric nanowalls were prepared with the replica molding technique and metal films, of comparable thicknesses, were then deposited on one side of the polymer nanowalls by vacuum process. During the metal deposition, the nanowalls themselves buckle laterally; this buckling is induced by the compressive residual stress in the metal film and geometric confining constraints. The feature of wrinkle patterns resulting from the lateral buckling was theoretically investigated using the scaling analysis. Theoretical results are in good agreement with the experimental observations.