Methacrylic acid (MAA) is investigated as a novel in situ interfacial modifier for styrene-butadiene rubber (SBR)/boehmite (BM) composite via a direct blending method. The reaction mechanism for the modification was revealed to be the BM/MM coordination and MAA/rubber grafting reaction. The substantiated BM/MAA coordination can improve the dispersion of BM in rubber matrix. It is illustrated that the ultimate mechanical performance and interfacial interaction are significantly enhanced by the in situ modification. The strong interaction between BM and SBR and the improved dispersion of BM in the rubber matrix are responsible for the largely enhanced mechanical properties. (C) 2011 Elsevier Ltd. All rights reserved.