Owing to inherent hydrophobicity, most polymer membranes suffer from serious fouling by organic pollutants, which severely deteriorates separation performances and reduce membrane lifetimes. Thus, surface hydrophilic modifications are essential to the development and application of various polymer membranes. Here, an unconventional but simple one-step approach was used to modify the surface of poly(vinylidene fluoride) (PVDF) membranes to produce good hydrophilicity and underwater superoleophobicity. This method directly anchored hydrophilic poly(vinyl alcohol) (PVA) onto PVDF membrane surfaces under γ-ray irradiation but without any vinyl additives. The obtained modified PVDF membranes possessed excellent separation performances for various oil-in-water emulsions, with oil rejection up to 99.5% and filtration flux up to 6.9 × 102 L m−2 h−1 bar−1 under ultralow pressure (0.084 bar). In addition, oil fouling was confirmed to be almost reversible on modified PVDF membranes, which made the flux recovery remarkably improved, from 33% of pristine PVDF membrane to 98% of modified membranes, and they also exhibited outstanding oil-fouling resistance to high viscosity oils. This study demonstrated that this unconventional radiation method was facile and effective for tailoring the performance of polymer membranes with saturated functional compounds, which could benefit the development of various functional membranes and other materials. Display omitted •High hydrophilicity and underwater superoleophobicity were endowed to PVDF membranes.•PVA was directly and covalently anchored on PVDF membranes through an unconventional radiation method.•PVA-modified PVDF membranes separated various oil-in-water emulsions.•PVA-modified PVDF membranes exhibited excellent anti-oil-fouling and easy-cleaning properties.