Acid (inorganic or organic) neutralization of bauxite residue has been one of the main approaches to reduce its alkalinity, which is largely caused by desilication products (DSP). However, the acid leaching mechanisms remain unsolved as they are complicated by complex mineralogy and different test conditions used in previous studies. In this study, bauxite residue and two DSP phases, zeolite Linde Type A (LTA) and sodalite, were leached using aqueous HCl solutions with concentrations ranging from 0 to 1 M. The leaching kinetics of Na, Al, and Si were measured, and solid samples were examined using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM) cross-section elemental mapping. The results reveal that DSP neutralization occurs in two stages: Na+-H+ ion exchange and hydrolysis of the Al-O-Si framework (dissolution of DSP). In the ion exchange stage, minimal Al and Si react compared with Na that readily dissolves. During the hydrolysis stage, reacted zeolite LTA converts to an amorphous phase while the sodalite aluminosilicate framework is dissolved.