Montmorillonite clay was modified with a new intercalation agent and was added with different amounts to the room-temperature-vulcanizing silicone rubber (RTV-SR) adhesive system. Both the reinforcing and compatibilizing performance of the filler were investigated using physicomechanical properties, wide angle X-ray diffraction (WAXD), Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). There was a remarkable increase of cohesive strength and tensile and thermal properties with the organic montmorillonite (OMMT) loading up to 10 parts per hundred of resin by weight (phr). It was proposed that the nanoreinforcing effect caused by the well-dispersed silicate layers may reduce the amount and size of voids and increase the length of the crack spread path during lap shear testing.