In this study; licorice root, which is a sustainable natural material with a low environmental waste load, is used as an alternative fire retardant (FR) material. Flammable retardancy properties of 100% cotton and 50% cotton-50% polyester blended woven fabrics were researched by using licorice root and commercial organic phosphorus-nitrogen and phosphorus including compounds. Flame retardancy and thermal decay behaviour of the cotton and cotton/polyester blended fabric samples were qualified by the vertical burning test, limiting oxygen index (LOI), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The findings revealed that licorice root extracts enhanced the thermal behavior of the cotton and cotton/polyester blended fabrics after padding and coating processes. The practices increased the amount of oxygen demand for combustion in the environment and besides they did not change the morphological properties of the fabric samples. As a result, the usage of licorice root extracts considerably improved the fabric’s flammability under test.