Rubber nanocomposites based on carboxylated acrylonitrile butadiene rubber and carboxylated styrene butadiene rubber (XNBR/XSBR) with different compositions (100/0, 80/20, 60/40, 40/60, 20/80 and 0/100) and various montmorillonite (OMMT) contents with compatibilizer dichlorocarbene-modified SBR (DCSBR) were prepared. The results of rheometric tests showed that with adding DCSBR compatibilizer and increasing OMMT, the optimum curing time and scorch time decreased. The X-ray diffraction analysis indicated adding DCSBR compatibilizer causes increase in distance between the layers of silicate plates in the rubber phase of nanocomposites compared to OMMT powder. This phenomenon was also confirmed by direct observation of the microstructure by a transmitted electron microscope. The addition of OMMT and DCSBR compatibilizer surprisingly increased the mechanical properties such as elongation at break, tensile modulus, tensile strength and fatigue strength of the XNBR/XSBR (80/20).