The inclusion of inorganic nano-fillers with high mechanical strength in polymers could enhance efficiently the nano-mechanical properties of polymer-matrix (nano) composites. In this article, low-cost, high mechanical strength and stable crystal structured Aluminum nitride (nano) particles were incorporated into a High-density polyethylene (HDPE) thermoplastic polymer-matrix fabricated by melt blending, compression moulding followed by hot pressing for investigation of nano-mechanical properties of HDPE/AIN nanocomposites. Nano-mechanical properties of HDPE/AIN (nano) composites (020 vol%) were measured by Quasi-static nanoindentation technique. A standard Berkovich indenter was used to make indentations under four different normal loads viz., 700, 1000, 3000 and 5000 mu N, respectively. The surface topographies of the indented regions were monitored by AFM. The microstructure of AIN (nano)/HDPE composites were characterized by intermittent tapping mode AFM, XRD, FEG-SEM and HR-TEM. The results showed that the homogenous distribution of AIN (nano) particles in the HDPE polymer-matrix affected the nano-mechanical properties of AIN (nano)/HDPE composites significantly. Nano-mechanical properties of the composites display substantial improvement with increasing AIN (nano) content in HDPE. The results are discussed with reference to AIN (nano) particles dispersion, interfacial adhesion and effective load transfer in AIN (nano) particles filled HDPE polymer composites. (C)2017 Elsevier B.V. All rights reserved.