AbstractIn‐situ interfacial polymerization technique is developed to prepare monovalent anion‐permselective membranes (MAPMs). The introduction of multi‐hydroxyl (OH) and cationic groups in the base membrane provide suitable routes towards the monovalent anion transport. Only trimesoyl chloride is employed to generate a crosslinked polyester layer on membrane surface. The ISIP transforms the surface of anion exchange membranes into a dense and negatively charged layer to promote the ion permselectivity. The modified membranes show a high limiting current density and low membrane resistance of 4.7 Ω cm2. The resultant membranes exhibit a high Cl− flux of 6.3 × 10−8 mol cm−2 s−1 and a high permselectivity of ~60 for Cl−/SO42−. The findings demonstrate the ISIP technique having great potentials for the fabrication of highly permselective MAPMs.