Mixed protein-surfactant systems are widely used for stabilizing emulsions in the food industry. This study investigated the effects of ultrasound pretreatment on the structural and functional properties of chickpea protein isolate (CPI) and its binding interaction with ginseng saponin (GS). Ultrasound pretreatment induced the unfolding of CPI and promoted the binding affinity of CPI to GS, which was confirmed by fluorescence spectroscopy. Circular dichroism spectra demonstrated that the addition of GS increased the α-helix content by 11.20% and reduced the β-sheet, β-turn and random coil content by 3.70%, 1.30% and 6.00%, respectively. Compared with the U0-GS complex, the U15-GS complex stabilized emulsions showed higher (P < 0.05) oxidative stability that the PV and TBARS values decreased by 101.81 and 8.88 mg/L, respectively. Moreover, ultrasound pretreatment significantly increased the interfacial adsorption of GS, antioxidant activity of CPI-GS complexes and the retention rate of astaxanthin, which accounted for the improved oxidative stability of emulsions. Generally, ultrasound was successfully applied to design emulsions with improved stability and nutritional properties in food systems. Display omitted •Ultrasound induced the structural changes of chickpea protein isolate (CPI).•Ultrasound enhanced the binding affinity of CPI to ginseng saponin (GS).•Ultrasound improved the antioxidant activity of CPI-GS complexes.•Ultrasound-treated CPI-GS complexes formed emulsions with smaller droplets.