In the recent years, rising interest has emerged in the use of inorganic nanofillers, such as silica, titania, alumina, and zirconia, to increase the rigidity, dimensional stability, and toughness of various polymeric matrices [1]. In the present work a high density polyethylene (HDPE) matrix was melt compounded with different amounts of surface functionalized fumed silica nanoparticles. The morphology, rheological behavior and mechanical response in a wide range of temperatures of the obtained nanocomposites were investigated. The effect of a thermo-oxidative ageing near HDPE melting temperature was also studied. SEM micrographs evidenced a homogeneous distribution of nanoparticles up to 10 wt% of silica. Above this point a percolated network is formed which is also highlighted by rheological analysis. A clear effect of the nanofiller content and dispersion state was observed on the tensile properties. The tensile creep behavior of the neat HDPE and nanocomposite materials was investigated in the temperature range from 25 to 100°C. In agreement with results reported by Dorigato and al [2], it was shown that the resistance to creep increased with the nanofiller content. After their initial characterization, samples were exposed to a thermo-oxidative ageing near HDPE melting temperature. The impact of increased ageing times on the materials structure, morphology and mechanical properties was determined and the main results will be discussed. [1]. F. Hussain, M. Hojjati, M. Okamoto, and R.E. Gorga, J. Compos. Mater., 40, 1511 (2006). [2]. Dorigato and al, « Thermo-mechanical properties of high density polyethylene – fumed silica nanocomposites: effect of filler surface area and treatment », Journal of polymer research, 2012