Polypropylene (PP)/nylon 11/maleated ethylene-propylene-diene rubber (EPDM-g-MAH) ternary polymer blends were prepared via melt blending in a corotating twin-screw extruder. The effect of nylon 11 and EPDM-g-MAH on the phase morphology and mechanical properties was investigated. Scanning electron microscopy observation revealed that there was apparent phase separation for PP/EPDM-g-MAH binary blends at the level of 10 wt % maleated elastomer. For the PP/nylon 11/EPDM-g-MAH ternary blends, the dispersed phase morphology of the maleated elastomer was hardly affected by the addition of nylon 11, whereas the reduced dispersed phase domains of nylon 11 were observed with the increasing maleated elastomer loading. Furthermore, a core-shell structure, in which nylon 11 as a rigid core was surrounded by a soft EPDM-g-MAH shell, was formed in the case of 10 wt % nylon 11 and higher EPDM-g-MAH concentration. In general, the results of mechanical property measurement showed that the ternary blends exhibited inferior tensile strength in comparison with the PP matrix, but superior toughness. Especially low-temperature impact strength was obtained. The toughening mechanism was discussed with reference to the phase morphology. (C) 2008 Wiley Periodicals, Inc.