Comprehensive fouling resistance, high permeability, high rejection, and robustness are indispensable criteria for advanced oil/water separation membranes intended for sustainable operation under harsh conditions. Accordingly, in the present study, a new class of zwitterionic-polyelectrolyte-grafted aliphatic polyketone (PK) membranes was prepared by the highly controllable surface-initiated atom transfer radical polymerization (SI-ATRP) of N-(3-sulfopropyl)-N-methacroyl-oxyethyl-N,N-dimethylammonium betaine (SBMA) on highly porous and hydroxylated PK membranes. The PK-g-PSBMA membrane prepared with 10-min grafting modification exhibited excellent solvent-resistant underoil superhydrophilicity as well as underwater superoleophobicity and ultralow protein adhesion. The low mass-transfer resistance, low fouling potential, and strong solvent resistance of the porous hydroxylated PK substrate along with the ultralow fouling nature of the zwitterionic SMBA layer, endowed the PK-g-PSBMA membranes with self-cleaning properties, sustainably high emulsion fluxes of 1200–1800 L m⁻² h⁻¹ bar⁻¹, low oil permeations at 6–33 ppm, and high flux recovery ratios of 82–98%, even for difficult micro- and nanoemulsions containing small oil droplets and complicated pollutants (surfactant, high salinity, and natural organic matters). Thus, PK-g-PSBMA membranes with simple preparation route and comprehensive performances show great potential for treatment of challenging oily wastewater.