This study evaluates the fire-retardant (FR) performance of polyester/ cotton (PC) and polyester/viscose (PV) fabrics treated with an alkyl phosphate ester-based FR agent at concentrations of 100, 150, and 200 g/l, followed by curing at 200 °C for 60 or 180 s. Untreated fabrics burned completely, whereas the FR treatment reduced flammability significantly, with char lengths of 2 cm (PC200C60t) and 0.4 cm (PV200C180t). The limiting oxygen index (LOI) increased to 22 % (PC) and 23 % (PV), confirming enhanced flame resistance. EDX and FTIR analyses confirmed successful FR deposition, showing increased phosphorus and nitrogen content alongside the formation of ester bonds (O-H, C=O, O-C-H). Bending stiffness rose by 29 % for PV200C180t, while wrinkle recovery improved by 27.9% (PC) and 23.3 % (PV). Air permeability decreased by 41.5 % (PC) and 59.5 % (PV), and water permeability (PDA) declined by 15.74 % (PC) and 35.61 % (PV). The treatment achieves an effective balance between flame resistance and wearability, demonstrating strong potential for protective textiles.