The aim of this study was to evaluate the effects of applying low replacement ratios (0.75% and 1.50% of the binder weight) of nano-SiO2 particles with different specific surface areas (200 and 380 m2/g) on the properties of high-performance concrete (HPC). Mechanical (compressive and splitting tensile strengths), electrical resistivity, non-destructive (ultrasonic pulse velocity), and microstructural (mercury intrusion porosimetry, X-ray diffraction, and scanning electron microscopy) tests were conducted to investigate the macroscopic and microscopic effects of nano-SiO2 particles on HPC characteristics. The results indicated that the performance of nano-SiO2 particles significantly depended on their specific surface areas and the water to binder (w/b) ratio of the mixtures. By decreasing the HPC w/b ratio from 0.35 to 0.25, the nano-SiO2 particles with lower specific surface areas performed better than the nano-SiO2 particles with higher specific surface areas. Microstructural investigations demonstrated that the decrease in efficiency of nano-SiO2 with higher specific surface area at a lower w/b ratio correlates to the formation of nanoparticle agglomerates, particularly at the higher replacement ratio of nano-SiO2 particles (1.5%). However, the influence on the compressive and splitting tensile strengths and electrical resistivity varied because of how the nano-SiO2 particle performance differences affected the mechanical and durability properties.