Thin-film composite polyamide (TFC-PA) membranes have recently been found to be highly capable of improving separation efficiency when subjected to surfactant-assisted interfacial polymerization (IP). There is a widespread belief that surfactants' ability to accelerate the diffusion of amine monomers, thereby promoting IP reactions, accounts for the improved performance. Through the IP and use of trimesoyl chloride (TMC) and m-phenylenediamine (MPD) on plasma-treated polyethylene (PE), this study investigates the utilization of anionic sodium dodecyl sulfate (SDS) surfactant for the development of TFC nanofiltration (NF) membranes. The alteration of the PA film structure induced by the various concentrations of SDS was thoroughly investigated using ATR–FTIR, water contact angle, zeta potential, FESEM, and AFM analyses. NF performance was then evaluated by testing four salt solutions, namely Na2SO4, MgSO4, MgCl2, and NaCl. Interestingly, the results revealed a notable influence of SDS micelles on the structure of the PA layer. Additionally, the introduction of SDS significantly affected the pure water flux during the NF process. Moreover, the rejection rates of salts were substantially enhanced upon increasing the concentration of SDS to 0.3 wt%. This study underscores the role of SDS in the preparation of NF membrane, highlighting its potential for improving membrane-based desalination prepared on hydrophobic supports.