Fly ash (FA) is produced as a waste byproduct during the burning process of coal in thermal power plants whose cost is primarily associated to cleaning and transportation. It possesses mechanical properties on account of its constituents like silica and alumina. The use of FA as filler in styrene butadiene rubber (SBR) was of researchers’ interest to reinforce and/or to reduce product cost. In this article, the physico-mechanical properties of SBR composites with varying amounts viz., 0, 5, 10, 15, 20 and 40 phr of FA contents were investigated. The physico-mechanical properties of the rubber vulcanizates were determined before and after heat aging at 90 ºC for 72h. It was observed that fly ash-filled SBR composites were better in mechanical properties such as elongation and resilience. Thermo gravimetric analysis (TGA) studies of the SBR/FA composites have been performed in order to establish the thermal stability and the mode of thermal degradation.TGA thermograms indicate multiple steps of the SBR/FA systems thermal degradation.