Abstract: Recycled brick fine aggregate (RBFA) was produced from waste clay red bricks and impregnated with polymer emulsion to form emulsion-modified brick aggregate (PRBFA). The effects of PRBFA substitution rate, emulsion impregnation method, emulsion solid content, and emulsion type on the damping properties of PRBFA-based mortar (PBM) were investigated. The damping characteristics of PBM were tested using suspended beam-free vibration tests, and the damping mechanism of PBM was analyzed based on the interface properties of PRBFA. The results demonstrate that the first-order damping ratio ( \xi ) and loss modulus (E′′) of PBM increase with the PRBFA substitution rate, showing maximum increases of 118.5% and 27.7%, respectively. Both \xi and E′′ of PBM increase with the emulsion solid content, with maximum increases of 85.9% and 29.0%, respectively. Polyvinyl alcohol emulsion significantly improves the damping effect of PBM, with a maximum increase of 164.9%. Different impregnation methods have a minor effect on \xi , but saturation impregnation followed by drying improves E′′ by 25.5% and increases the compressive strength of PBM by 26.3%. When the PRBFA replacement ratio is 50%, PBM exhibits optimal performance in both strength and damping properties. The emulsion's viscoelastic properties and weak adhesion with the inorganic cement matrix, form a constrained-layer damping structure, facilitating viscous sliding at the weak interfaces and enhancing PBM's damping characteristics.