Abundant textile waste has raised increasing concerns worldwide in developing novel circular textiles approach. This study investigated the optimum cellulase production from textile waste by Aspergillus niger CKB. Textile wastes consisting of cotton and polyester in various ratios were used as low-cost feedstock. Three types of cultivation media were compared in solid state fermentation and Mandels medium with yeast extract selected due to its superior cellulase production. Conditions including moisture, pH, inoculum size and organic nitrogen were evaluated and optimised via response surface methodology. Supplementary carbon sources and cellulase inducers were also employed to enhance fungal growth and cellulase production. The results indicated that the optimised fermentation method significantly improved cellulase producing efficiency and enzyme activity by 88.7% and 25.8%, respectively. The maximum cellulase activity reached 1.56 FPU g−1 in 6 days. The outcomes led to the efficient recovery of glucose and polyester, which could contribute to a closed-loop recycling strategy for the textile industry, and enable the transition to an advanced circular textiles economy.