The study examined the impact of salt stress on carnation plants and the efficacy of silicon dioxide nanoparticles (SiO2-NPs). Two trials manipulated salinity levels (0, 20, 40, and 60 mm) and SiO2-NPs concentrations (0, 25, and 50 mg L−1). Elevated salinity resulted in decreased growth, root development, and flowering traits while accelerating flowering time and increasing Na+ and Cl− content and superoxide dismutase (SOD) enzyme activity. Conversely, SiO2-NPs application improved growth parameters, root development, and flowering traits, enhanced leaf chemical composition and catalase (CAT) enzyme activity, and mitigated negative effects compared to the control. The 25 mg L−1 SiO2-NPs treatment proved most effective in alleviating salt stress. These findings indicate SiO2-NPs could be valuable in mitigating salt stress impacts on carnation plants.