LAUSR

High‐performance polyamide (PA) composite membranes prepared via interfacial polymerization (IP), the use of cosolvents to enhance the solubility of aromatic amine monomers has gained significant attention. However, previous attempts often required high cosolvent concentrations (>50 wt%), which compromised membrane performance. This study demonstrates that a low concentration of N , N ‐dimethylformamide (DMF) as the cosolvent in the water phase is sufficient to promote the formation of a uniform and thin PA layer (20.3 ± 2.07 nm) on the porous substrate. The effects of DMF concentration were investigated. The introduction of DMF significantly enhances interfacial stability and alters diffusion dynamics. The membrane formed with 30% DMF exhibits a high methanol permeance of 22.4 L m −2 h −1 (LMH) bar −1 along with 99.2% rejection of rose bengal (RB). The smooth surface morphology significantly improves the membrane anti‐fouling properties. The study demonstrates a facile cosolvent‐assisted IP process to fabricate the high‐performance thin film composite (TFC) membrane, which has wide applications in organic solvent nanofiltration.