Highly oriented polymer nanoribbons are prepared by tape extrusion of a phase-separated polymer blend into thin film and by subsequently dissolving the continuous polymer phase from it. The nanoribbons aligned well along the extrusion direction with the flat faces parallel to the film surface. Their thickness and width are controllable in the range of 65–200 nm and 170 nm–1.23 μm, respectively, by adjusting the ratio of the two polymers in the blend and processing parameters. Without dissolving the continuous phase, the nanoribbon-containing film shows interesting structural color, chatoyancy, and light polarization effects, and anisotropic mechanical strength. Tape extrusion of phase-separated polymer blend may offer a simple, scalable way to prepare highly oriented nanoribbons and functional films.