The aim of the present study was to investigate the effect of nano-SiO2 particles with different specific surfaces areas (200 and 380 m2/g) on mechanical properties of fiber-reinforced high-performance concrete (FRHPC) produced with two different types of fibers including steel and polypropylene fibers. Accordingly, different mechanical tests (compressive, splitting tensile and flexural strengths) as well as electrical resistivity were performed at 7, 28, and 91 curing days. In addition, the modulus of rupture and toughness of HPC prisms was calculated based on the flexural testing results. Also, after performing the flexural test, HPC fragments were selected for scanning electron microscopy (SEM) test to evaluate the microstructural performance of nano-SiO2 particles in the matrices of HPC and FRHPC. Results demonstrated that the application of nano-SiO2 particles can enhance the mechanical and electrical resistivity properties of HPC and FRHPC. In addition, the coarser type of nano-SiO2 showed better performance in increasing the mechanical properties of HPC with or without fibers (steel and polypropylene) than finer one. However, the finer type of nano-SiO2 particles resulted in higher electrical resistivity in HPC and FRHPC specimens compared to coarser type. Moreover, according to SEM test, the enhancement of mechanical properties of HPC and FRHPC in the presence of nano-SiO2 particles could be related to densification of the matrix by fourfold performance of these particles.