Soil and water salinity are considered among the main abiotic constraints especially in arid and semi-arid regions where saline groundwater is often used for crop irrigation since surface water is not easily available. The aim of the present investigation was to study the effects of low (25 mM NaCl) and moderate (50 mM NaCl) salinity on Zinnia marylandica (Double White cultivar) growth, water status, potassium and sodium contents, as well as K⁺/Na⁺ ratios. Plants were grown on inert sand and irrigated with one fourth-strength Hoagland's nutrient solution for 38 days under greenhouse conditions. Three treatments were considered: control (0 mM NaCl), low salinity (25 mM NaCl), and moderate salinity (50 mM NaCl). At the harvest, inflorescences were collected then plants were cut into shoots and roots. Results indicated that inflorescences produced under saline conditions were smaller than those produced under control conditions, but they maintained the same number per plant, water content, and days to first opening. In addition, whole plant dry weight decreased with the increasing salinity with no variation in root/shoot ratio. A preferential allocation of K⁺ to shoots and Na⁺ to roots was also observed, leading to higher K⁺/Na⁺ ratio in shoots. Moreover, shoot K⁺/Na⁺ ratio decreased with salinity. Based on these results, it could be concluded that Zinnia marylandica lacks the ability to maintain K⁺/Na⁺ ratio at an adequate level at higher salinity levels.