The removal of arsenic-bearing minerals from concentrates is an important environmental objective, especially in relation to metallurgical processing. In this regard, there has recently been interest in the effects of ionic species on the flotation performance of minerals in liquid phases. While arsenopyrite is depressed by Fe3+, the depression mechanism involving Fe3+ during arsenopyrite flotation has not been researched in detail. Herein, we report an investigation into the adsorption of ferric ions on arsenopyrite surfaces and its implications for flotation, using micro-flotation and zeta-potential experiments, local electrochemical impedance spectroscopy, and X-ray photoelectron spectroscopy. The results reveal that Fe3+ exists in solutions in different forms and its absorption onto the arsenopyrite surface leads to a decrease in zeta potential and an increase in impedance. Meanwhile, the Fe, As, and S on the mineral surface are oxidized, with oxidation more obvious with increasing pH. The oxide residues on the surface of the arsenopyrite decrease its floatability.