The aim of the study is to evaluate the performance of Hot Mix Asphalt (HMA) and bitumen by modifying bitumen with nano materials according to Superpave mix design procedure. In this study, bitumen is modified by silica nanopowder (SiO2NP). Nano powders are mixed with base bitumen at contents of 0.1, 03 and 0.5% by weight. Rutting and fatigue performance of bitumens are determined. HMA is prepared with nano modified bitumens at optimum binder content (OBC). Moisture susceptibility of modified HMA is evaluated according to Modified Lottman test procedure. Nano modified bitumens are also evaluated by scanning electron microscopy (SEM) whether the modification is uniform or not. As a result, better performance is obtained by SiO2NP at a content of 0.3% modification. Performance Grades (PG) of all modified bitumens are determined as PG 64-22. OBCs are decreased by modification. HMA sample modified by SiO2NP at a content of 0.3% is determined 26.25% higher resistive to moisture compared to reference sample. Homogenous mixture is obtained according to SEM results. It is found that the agglomeration of nano materials is mostly lower than 4 mu m in the mixtures. As a result, SiO2NP 0.3% shows satisfying results. (C) 2017 Elsevier Ltd. All rights reserved.