We report on the preparation of nanoporous films based on an amphiphilic graft copolymer of poly(vinyl chloride-graft-methyl methacrylate), i.e., PVC-g-PMMA. The PVC-g-PMMA graft copolymer was synthesized via atom transfer radical polymerization (ATRP), as confirmed by nuclear magnetic resonance spectroscopy (1H NMR), Fourier transform-infrared (FT-IR) spectroscopy, and gel permeation chromatography (GPC) analysis. The PVC-g-PMMA graft copolymer molecularly self-assembled into nanophase domains of PVC main chains and PMMA side chains, as revealed by wide angle X-ray scattering (WAXS) and transmission electron microscopy (TEM). The graft copolymer film prepared from tetrahydrofuran (THF), a good solvent for both chains, had a random microphase-separated morphology. However, when prepared from dimethyl sulfoxide (DMSO), a solvent selectively good for PVC, the film exhibited a micellar morphology consisting of a PMMA core and a PVC corona. Nanoporous films with different pore sizes and shapes were prepared through the selective etching of PMMA chains using a combined process of UV irradiation and acetic acid treatment.