In this study, we report the synergistic effect of nanoclay and maleic anhydride grafted polyethylene (PE-g- MA) on the morphology and properties of (80/20 w/w) nylon 6/high density polyethylene (HDPE) blend. Polymer blend nanocomposites containing nanoclay with and without compatibilizer (PE-g-MA) were prepared by melt mixing, and their morphologies and structures were examined with scanning electron microscopy (SEM) and wide angle X-ray diffractometer (WAXD) study. The size of phaseseparated domains decreased considerably with increasing content of nanoclay and PE-g-MA. WAXD study and transmission electron microscopy (TEM) revealed the presence of exfoliated clay platelets in nylon 6 matrix, as well as, at the interface of the (80/20 w/w) nylon 6/HDPE blend-clay nanocomposites. Addition of PE-g-MA in the blend-clay nanocomposites enhanced the exfoliation of clays in nylon 6 matrix and especially at the interface. Thus, exfoliated clay platelets in nylon 6 matrix effectively restricted the coalescence of dispersed HDPE domains while PE-g-MA improved the adhesion between the phases at the interface. The use of compatibilizer and nanoclay in polymer blends may lead to a high performance material which combines the advantages of compatibilized polymer blends and the merits of polymer nanocomposites. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 1801-1811, 2012