Polyethersulfone thin film nanocomposite membrane was prepared via an innovative real-time casting-coating (RTCC) method. The formation of thin film embedded by nano-additives was along with casting the sublayer with the aid of a specialized casting knife. The current work aimed to prepare a thin layer on the membrane containing chitosan and cellulose nanocrystal nanofillers to compare the TFN PES membrane performance with mixed matrix ones. The permselectivity toward colored water by acid orange 7 (AO) and methylene blue (MB) dyes, as well as the morphological investigation of prepared membranes, were used to examine the applicability of the suggested RTCC method. Based on the results the CNC-modified membranes casted via RTCC method offered higher water flux and dye removal. Also, chitosan nanoparticles would be more efficient additives for PES membranes when they were mixed with a top-layer casting solution instead of whole membrane bulk. Significantly higher water flux (around 2 fold) and dye removal confirmed the preference for the introduced method of RTCC to prepare TFN membranes for efficient nanofiltration uses.