In this study, we investigated the effects of SiO2 nanoparticles (SiO2-NPs) (1, 10, 25, 50, and 100mg/L) for 24h in vitro on the motility parameters and oxidative stress markers such as total glutathione (TGSH), catalase (CAT), and malondialdehyde (MDA) of rainbow trout, Oncorhynchus mykiss sperm cells. Therefore, SiO2-NPs were synthesized with sol-gel reaction from tetraethoxy orthosilicate (TEOS). The prepared nanoparticle structures were characterized for chemical structure, morphology and thermal behavior employing Fourier transform infrared spectroscopy, X-ray spectroscopy, scanning electron micrograph, and thermal analysis (DTA/TGA/DSC) techniques. After exposure, there was statistically significant (p<0.05) decreases in velocities of sperm cells. CAT activity significantly (p<0.05) decreased by 9.6% in sperm cell treated with 100mg/L. In addition, MDA level significantly increased by 70.4% and 77.5% in sperm cell treated with 50 and 100mg/L SiO2-NPs, respectively (p<0.05). These results showed that SiO2-NPs may have toxic effect on rainbow trout sperm cells in 50mg/L and more.