Halogen free flame retardant cotton (FR cotton) fabric was prepared by grafting 2,3-epoxypropyl methacrylate (GMA) on ordinary or untreated cotton (UT cotton) fabric by γ-rays from 60Co source. Epoxy groups present in GMA grafted cotton (GMA-g-cotton) fabric was reacted with ethylene diamine and subsequently modified with orthophosphoric acid solution to convert in to FR cotton fabric. Effects of imparted dose, concentration of monomer on grafting percentage were studied. The changes in thermal properties after treatment were investigated by using Thermo gravimetric analyser. Limiting oxygen index, char length, time after glow and time after flame were also studied as per ASTM D2863 and IS11871, respectively, for both FR cotton and UT cotton fabrics. The FR cotton fabric was found to pass all the above tests. Washing durability of the FR cotton fabric in different cleaning agents was also studied and a washing solution containing organic solvent mixture is suggested.