Soft liners are designed to modify the surfaces of prostheses that interact with the soft tissues of the mouth to improve denture performance. Usually, the denture soft lining material must be replaced every 6-12 months since it deteriorates with time when exposed to an oral environment. Recently, researchers have been primarily concerned with improving soft liners' properties by incorporating different fillers into a polymeric matrix to create new materials that can tolerate oral conditions while maintaining flexibility. This study aimed to examine the impact of incorporating various weight concentrations of cerium oxide nanoparticles on some mechanical and physical properties of an acrylic-based heat-cured soft denture liner.