This study investigated the feasibility of using textile waste as feedstock for cellulase production through solid state fermentation. Aspergillus niger CKB was selected with the highest cellulase activity (0.43 ± 0.01 FPU g−1) after 7 days of cultivation on pure cotton. Material modification techniques including autoclaving, alkali pretreatment and milling were applied on six types of textiles with various cotton/polyester blending ratios. The results indicated that using autoclaved textile blending cotton/polyester of 80/20 led to the highest cellulase activity (1.18 ± 0.05 FPU g−1) with CMCase, β-glucosidase and avicelase activities of 12.19 ± 0.56 U g−1, 1731 ± 4.98 U g−1 and 2.58 ± 0.07 U g−1, respectively. The fungal cellulase was then extracted and applied to textile waste hydrolysis, in which a sugar recovery yield of 70.2% was obtained. The present study demonstrates a novel circular textile waste-based biorefinery strategy with recovery of glucose and polyester as value-added products.