Kaolin is a naturally abundant and cheap ore, which can impart various properties to rubber composites besides lowering its cost. In this work, kaolin and thermally treated kaolin (especially m-kaolinite), which is the most active species of kaolin were added to styrene–butadiene rubber composites in different concentrations ranging between 10 and 50 phr to study their effect on SBR rheometric, physical, mechanical, and thermal properties. The main aim of this study was to state whether the activity of calcined kaolin will allow it to work as a bifunctional additive (i.e., reinforcing filler and accelerator) or an adverse one (i.e., working as an active radical breaking the polymer chains). The study revealed that SBR containing calcined kaolin performed better properties than those containing kaolin indicating that calcined kaolin worked as a bifunctional additive in SBR composites.