In this study, the effect of municipal solid waste (MSW) incineration ash, such as a mixture of fly ash and bottom ash as filler in epoxy composite, was studied for characterisation of mechanical properties such as flexural and tensile strength. Investigation was carried out by varying concentrations of MSW incineration ash and surface treating of incineration ash powders by using colloidal mesoporous silica (CMS) nanoparticles. The results suggested that the tensile and flexural strengths of the composites improved with the incorporation of incineration ash treated with CMS nanoparticles, indicating the CMS nanoparticles enhanced adhesion in the bonding enhancement of incineration ash with polymer resins. XRD analysis showed that surface treatment of MSW incineration ash with colloidal mesoporous silica removed soluble salts found in MSW incineration ash. In addition, it was found that carbonation reaction occurred during the reaction of MSW incineration ash and CMS nanoparticles due to the formation of predominantly calcium carbonate. The carbonation reaction would promote CO2 sequestration. Outcomes of the leaching test indicated that heavy metals such as Pb, Zn, Fe, and Cr were immobilised into the matrix of CMS-treated MSW incineration ash. Hence, reuse of MSW incineration ash as reinforcing filler in the composite appears to be a promising opportunity to obtain valuable raw material from municipal solid waste and reduce the dependence on natural mineral fillers