In the present study, the fracture properties of different types of organophilic montmorillonite (OMMT) filled polyamide 6/polypropylene nanocomposites was investigated. Two types of compatibilizers, i.e., maleic anhydride grafted polypropylene (PP-g-MA) and maleic anhydride grafted styrene-ethylene/butylene-styrene (SEBS-g-MA) were used to compatibilize these systems. The tensile properties were studied through tensile test at two different testing speeds; 50 and 500 mm/min whereas the fracture properties were determined using single-edge-notch-3 point-bending (SEN-3PB) specimens at three different testing speeds; 1, 100, and 500 mm/min. The presence of both PP-g-MA and SEBS-g-MA compatibilizers improved the tensile and fracture properties of nanocomposites due to the compatibilizing effect of both compatibilizers. SEBS-g-MA compatibilizer seemed to be more effective in improving the fracture toughness of nanocomposites than PP-g-MA especially at high testing speed. This was due to the elastomeric nature of SEBS-g-MA, which can provide a better toughening effect than the relatively harder PP-g-MA. POLYM. ENG. SCI., 50:1493-1504, 2010. (C) 2010 Society of Plastics Engineers