In this article, polyamide 6 (PA6), maleic anhydride grafted ethylene-propylene-diene monomer (EPDM-g-MA), high-density polyethylene (HDPE) were simultaneously added into an internal mixer to melt-mixing for different periods. The relationship between morphology and rheological behaviors, crystallization, mechanical properties of PA6/EPDM-g-MA/HDPE blends were studied. The phase morphology observation revealed that PA6/EPDM-g-MA/HDPE (70/15/15 wt %) blend is constituted from PA6 matrix in which is dispersed core-shell droplets of HDPE core encapsulated by EPDM-g-MA phase and indicated that the mixing time played a crucial role on the evolution of the core-shell morphology. Rheological measurement manifested that the complex viscosity and storage modulus of ternary blends were notable higher than the pure polymer blends and binary blends which ascribed different phase morphology. Moreover, the maximum notched impact strength of PA6/EPDM-g-MA/HDPE blend was 80.7 KJ/m2 and this value was 1011 times higher than that of pure PA6. Particularly, differential scanning calorimetry results indicated that the bulk crystallization temperature of HDPE (114.6 degrees C) was partly weakened and a new crystallization peak appeared at a lower temperature of around 102.2 degrees C as a result of co-crystal of HDPE and EPDM-g-MA. (c) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013