Peanuts are one of the most important food allergens globally. To reduce the risk of allergies, peanuts were treated with cold plasma (CP) for varying durations. The impact of CP on the immunoreactivity, structure, and functional properties of peanut protein (PP) was investigated, aiming to comprehensively evaluate the influence of CP on PP. The results showed that following a 25-min CP treatment, the immunoreactivity of PP decreased by 69%, with improved digestibility. The analysis of the secondary structure demonstrated a reduction of 2.32% in α-helix and 1.54% in random coil, accompanied by an increase of 4.12% in β-sheet. This result indicated the disruption of the secondary structure in protein. Furthermore, the decrease in the intensity of intrinsic fluorescence, coupled with the rise in UV and extrinsic fluorescence, represented the fluorescence quenching of Trp and the exposure of hydrophobic groups. These alterations in structure, caused by the oxidation of CP, were postulated as potential contributors to the diminished immunoreactivity of PP. In addition, these structural modifications could augment the degree of adsorption at the air-water interface, resulting in a notable enhancement in the foaming capability of PP (from 152% to 213%).