Alumina particles is a ceramic powder used as a dispersed phase or filler to reinforce the mechanical properties and improve thermal properties of natural rubber foams via the vulcanization process at curing temperature 150 degrees C with a two-roll mill. The amount of alumina added in natural rubber foams were varied from 0 to 60 phr on 100 phr of natural rubber in a sulfur curing system. The sodium bicarbonate (NaHCO3) and N, N'-dinitrosopentamethylenetetramine (DNPT) were used as foaming agents. The sponge rubber composite foams were characterized for the microstructure, phase formation, thermal property, particle size distribution, and mechanical property by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetric analyzer (TGA), particle size analyzer, and compression set testing. The fabricated sponge rubber composite foams have distinctive characteristics such as light weight and good mechanical and thermal properties suitable for energy absorption such as thermal, noise, and vibration.