This study investigated the effects of silicon (Si) nutrition on hydroponically grown Zinnia elegans under salinity stress. In this study, six treatments, the control (basal nutrients without NaCl or Si), Si 50 (1.8 mM), Si 100 (3.6 mM), NaCl 50 (50 mM), Si 50 + NaCl 50 (1.8 mM Si; 50 mM NaCl), and Si 100 + NaCl 50 (Si-3.6 mM + NaCl-50 mM), were employed. After 15 days of treatment, growth parameters, biochemical measurements, and antioxidant enzyme activities were examined. Salinity stress significantly reduced plant growth, biomass, photosynthetic parameters, and pigments, and increased the electrolyte leakage potential (ELP), lipid peroxidation, and hydrogen peroxide level. Interestingly, with Si supplementation, Z. elegans recovered from salinity stress. Si enhanced growth and photosynthesis, and prevented the decomposition of photosynthetic pigments. Moreover, the addition of Si increased membrane integrity, thereby reducing the ELP and lipid peroxidation levels under salinity stress. Furthermore, Si modulated the activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and guaiacol peroxidase (GPX) in scavenging excess reactive oxygen species (ROS). Additionally, Si increased the macronutrient and micronutrient contents. Therefore, augmentation with Si provided salinity resistance and enhanced the growth of Z. elegans. © 2015, Korean Society for Horticultural Science and Springer-Verlag GmbH.