Hydrogels can be applied in fields like agriculture, medicine, food, and textiles because of their unique qualities. The high water-absorbing hydrogel can also be used to extinguish the flame. Approximately 90% of the hydrogel is made of water, which has a high heat capacity and enthalpy of vaporization. A significant quantity of heat energy is absorbed when the hydrogel is exposed to fire as water evaporates, thus quenching the flame. Further, the hydrogel network starts to contract, and any water or other solution inside is removed to the outside when the temperature of the volumetric phase transition is exceeded. Hence, the main objective of this study is to develop hydrogel-coated, flame-retardant (FR) cotton fabric using Polyvinyl alcohol (PVA) and Ortho-phosphoric acid (OPA). The OPA acts as a cross-linking and flame-retardant agent for the cotton fabric, which is the unique feature of this study. The cotton fabric is coated with PVA/OPA solution in varying concentrations and then tested for its flame retardancy, water absorption behavior, and other properties such as tensile, tear strength, bending rigidity, and thermal stability (TGA). Comparing all test samples in distilled water, the 20% PVA/10% OPA sample exhibited a better absorption percentage, which prevents it from being ignited by flame. This sample exhibited better tensile and tear strength with less bending rigidity than other samples. Hence, the developed 20% PVA/10% OPA sample can become better flame retardant fabric.