<p>The study delves into the multifunctional properties of PES membranes incorporated with carbon nanotubes (CNTs) prepared by non-solvent induced phase separation with combined crystallization-diffusion technique (NIPS-CCD). The SEM analysis revealed uniform fine porous, compact structure, suppressing macro-voids in the NIPS-CCD approach in comparison with NIPS membranes. The morphological observations disclosed that at 0.5 wt% of CNTs the sample displayed a tight skin layer with an elongated finger-like structure with finer pores. At an optimal composition of 0.5 wt% of MWCNTs in PES, the NIPS-CCD method displayed enhanced strength, stiffness and semi-ductile failure. This proves that NIPS-CCD technique refines pore structure, promotes dense skin formation which leads to improved mechanical integrity by maintaining interconnected pores. The BET analysis confirmed that NIPS-CCD coupled with CNT inclusion showed significantly higher surface area (5.845 m²/g), smaller pore size (19 Å), and optimized pore distribution in comparison with NIPS membranes. TGA analysis explored a thermally strong CNT network and stable interfacial interactions which have constrained the polymer chains and create a barrier effect delaying thermal decomposition. This was further confirmed with T_g shift towards higher values in DSC analysis specifically for NIPS-CCD membranes reflecting reduced mobility of PES chains, dense polymer packing, and decreased free volume. The optimized pore size distribution, refined pore structure, improved surface area, tensile strength, modulus and thermal stability of PES/CNT membranes prepared via NIPS-CCD approach could be well suited for advanced ultrafiltration wastewater treatment applications. The PES/CNT membrane fabricated via the NIPS-CCD method showed superior performance with a pure water flux of 126 L m⁻²&#xa0;h⁻¹, permeability of 84 L m⁻²&#xa0;h⁻¹&#xa0;bar⁻¹, low total flux loss (12.6%), and high FRR (98.4%), indicating enhanced permeation and antifouling properties.</p>