Most of textiles in use have limiting oxygen index (LOI) lower than 21, while cotton have 18.9, which means that they can burn easily once the fire has started. Currently, there is some difficulty in making durable flame retardant (FR) treatments for cotton fabric using an ordinary one-step wet process, which are nontoxic to the environment and humans. The goal of this research is to impart cotton fabrics flame retardant properties via partial carboxymethylation followed by ester crosslinking with phosphoric acid in presence of urea. This research has also aimed to investigate the optimum treatment conditions that allow the selective and controlled deposition of urea onto carboxymethylated cotton fabric. In this regards the effect of process parameters on the physicochemical and performance properties of treated cotton fabric will elucidate. The treated fabric were monitored for nitrogen and phosphorous content besides, limiting oxygen index (LOI), char length, char residue, whiteness index, retained tensile strength and elongation at break. The treated cotton fabrics show LOI and char length 38, 4.7 cm respectively, compared with 18 and 11 cm for untreated fabric. The existence of new polyphosphate-cellulose interaction and other functional groups introduced into cotton fabrics were confirmed by FTIR spectroscopy and TGA.