In this study, poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) dual-layer membranes filled with cellulose nanowhisker (CNWs), were fabricated by employing an integrated method combining water vapor-induced and crystallization-induced phase inversions. Four membranes (denoted as C-neat, C-I, C-II, and C-III) loaded with CNWs in the range of 0-3 wt% were prepared and characterized using various materials research aspects. The use of CNWs fillers was found to synergize the precipitation of the polymer layers in the integrated water vapor-induced and crystallization-induced method. With morphological examination, the C-III membrane showed prominent and well-laminated two layers structure, evidencing the great precipitating effect of 3 wt% CNWs on the crystallization the polymeric layers. The increase in CNWs loadings was found to improve the membrane porosity with, which was accompanied by a decrease in the pore size. The heat resistance of C-neat membrane was enhanced by CNWs loading of 1 wt% (C-I) whereas it decreased with loadings of 2 and 3 wt% (C-II and C-III) due to flaming behaviour of sulphated nanocellulose. Furthermore, The C-III membrane displayed the best mechanical properties in with respect to tensile strength, elongation at break and Young’s modulus compared to other membrane samples. For wastewater filtration performance, the continuous operation test showed that C-III membrane exhibited the highest removal efficiency for both Co2+ and Ni2+ metal ions reaching 83 and 84%, respectively. Thus, it can be concluded that CNWs filled dual-layer membranes have a strong potential for future development for the removal of heavy metal ions from wastewater streams.