Despite the high efficiency of polymer flooding as a chemical enhanced oil recovery (CEOR) technique, the low thermal stability and poor salt resistance of widely applied partially hydrolyzed polyacrylamide (HPAM) limited the application of this technique in oil reservoirs at harsh reservoir conditions of high–temperature and high–salinity (HTHS). These inadequacies of HPAM, result in the urge for an environmentally friendly polymer with good viscosifying properties and a substantial effect on mobility ratio at HTHS reservoir conditions. In this research, a high oleic acid waste vegetable oil (WVO) is utilized to synthesize a novel environmentally benign, thermo-responsive amphoteric nanocomposite for EOR applications at HTHS reservoir conditions. A green route transesterification reaction has been utilized to synthesize a novel thermo-sensitive monomer from WVO. The existence of unsaturated fatty acids isolated double bonds and acryloyl functional groups in the synthesized monomer has been confirmed using different characterization methods. The reactive acryloyl double bond in the synthesized monomer has been copolymerized with acrylamide, acrylacyloxyethyltrimethyl ammonium chloride, and 2-acrylamide-2-methylpropane sulfonic acid in presence of dimethylphenylvinylsilane via free radical emulsion polymerization. The synthesized nanocomposite has been characterized by FTIR, 1H NMR, SEM, EDX, TEM, and DLS. The thermal stability of the nanocomposite has been evaluated by TGA and DTA analysis. The results indicated that nanocomposite solution exhibited a pouncing thermo-thickening behaviour and superior viscosifying properties even at an ultra-low polymer concentration of 0.04 wt.% as the temperature increased from 25 to 100 ◦C, with increasing salinity from 10,000 to 230,000 ppm as well as salt-free solutions. Flooding experiments demonstrated that the oil recovery factor reached 15.4±0.1 % using low nanocomposite concentrations of 0.04 wt.%, 22.6±0.3 % using nanocomposite concentrations of 0.06 wt.% and 25±0.2 % using 0.1 wt.% nanocomposite concentrations evaluated under hostile conditions of 100 ºC and salinity of about 230,000 ppm. This research offers a new direction for the synthesis of a novel green, high molecular weight thermo-responsive nanocomposite for EOR application at extremely harsh reservoir conditions via WVO valorization.