With the ever-growing demand for protein, that is produced sustainably and economically maintaining environmental equilibrium, new concepts of food production where waste is efficiently utilized and transformed into value-added products are drawing the attention of many researchers. Hence a study was designed to utilize defatted groundnut oilseed cake – a byproduct of oil industry to produce protein isolates. The research investigated the impact of pH on the properties of protein isolates derived from defatted groundnut cake. Cold-pressed defatted groundnut cake was used to generate groundnut protein isolates using alkaline extraction (pH 7.0, 8.0, 9.0, 10.0, 11.0, and 12.0) and acid precipitation at pH 4.5. The protein content of defatted flour was 50.75±0.03% which significantly increased in all protein isolates, with highest protein content (88.76±0.50%) observed in isolates extracted at pH 7. The highest isolate recovery and protein yield were observed at pH 12 (61.22±0.01g/100g), (94.44±0.13%). The highest WHC and OAC concentrations were found in protein isolates extracted at pH 12 (1.44±0.0 g/g, 1.28±0.01 ml/g) respectively. The highest emulsion activity was reported at pH 8 (50.10±0.1%), but ES was higher in GPIs extracted at pH 7 and 9 (48.61±0.04% and47.34±0.02%). Bulk density and tapped density were higher in defatted flours than in protein isolates. Tapped density decreased in all protein isolates, as pH increased. Protein isolates from defatted peanut flour had low foaming and gelation capacities. The protein isolates extracted at various pH levels, had potential functional properties which are suitable for various product formulations. Hence, depending on the desirable functional property needed, the extraction of protein isolates can be taken up to develop various protein rich products. The alkaline extraction of protein isolates from plant sources presents a range of challenges, including quality control, pH optimization, denaturation risks, co-extraction of undesired compounds, and management of various process complexities. Addressing these challenges through meticulous control, conducted extensive experimentation within the pH range and innovative techniques contributes significantly to the food industry by advancing sustainable protein sources, improving food quality, and enhancing nutritional value. This optimization of extraction processes not only positions plant-based protein isolates as valuable alternatives to animal-derived counterparts but also promotes resource efficiency and reduced environmental impact. Together, these efforts pave the way for the development of nutritious, environmentally sustainable, and economically viable protein-rich food products to meet the ever-growing global demand.