Fast dissolution of nonmetallic inclusions such as alumina particles in molten slags has been required in secondary steelmaking-ladle and tundish-to minimize the amount and the size of nonmetallic inclusions in steel products. In the present work, the dissolution behavior of alumina particles in molten CaO-Al₂O₃ and CaO-Al₂O₃-SiO₂ slags at the temperatures between 1 500 and 1 550°C have been investigated in terms of kinetics and mechanism. Alumina particles were added directly into the slags and the variation of the particle size with time was determined using optical and electron microscopes. The conventional types of slag for ladle and tundish were included in the dissolution study. The effects of Al₂O₃, SiO₂, CaF₂ and MgO contents on the dissolution rate of alumina particles have also been determined. The diffusion boundary layer between alumina particle and bulk slag phase was observed and analyzed using SEM and EDS. Based on the analysis of kinetic data and the boundary layer, the dissolution mechanism has been discussed.