The effect of functionalized styrene-butadiene rubber (SBR) with glycidyl methacrylate (GMA) monomers, in the presence of styrene comonomers (SBR-g-GMA-co-St) as a compatibilizer on physical-mechanical, morphological, and swelling behavior of SBR/nitrile butadiene rubber (NBR) blends were studied. It was proved that the compatibilizer made through dicumyl peroxide-induced reaction which possessed 1.5 phr GMA in addition to 1.5 phr styrene comonomers showed higher efficiency of grafting. Possible in situ reactions between SBR-g-GMA-co-St and NBR component also were evaluated with an attenuated total reflectance mode of Fourier-transform infrared spectroscopy. SBR/NBR blend containing compatibilizer with a middle value of grafting demonstrated the most reactions between components. Dynamic mechanical thermal analysis results illustrated that the presence of SBR-g-GMA-co-St caused a significant improvement in compatibility of two components. This was verified with the scanning electron microscope pictures in which a smoother surface of the sample was clear. The enhancement in microstructure led to an increase in tensile strength, elongation at break, and storage modulus. Moreover, the increase in the intermolecular cross-links and made interactions considerably affected blends' swelling behavior in both hydrocarbon solvents (carbon tetrachloride and chloroform).