In this study, it was aimed to investigate the effects of salinity, which is an important environmental problem, in the cultivation of ornamental plants (such as zinnia) and irrigation with high salt water, especially on the antioxidant defense mechanism. For this purpose, the two Zinnia species were irrigated by different concentrations of saline water (50, 100, 150, 200 mM NaCl); effects of salinity on superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) lipid peroxidation (MDA) and hydrogen peroxide (H2O2) in the leaves were determined. The results showed that salinity conspicuously increased SOD, CAT, GR, H2O2 and MDA content at two Zinnia species compared to the control groups. It was found that SOD and CAT enzyme activities increased remarkably with 150 mM NaCl in both Zinnia species, but decreased with 200 mM NaCl.The highest GR enzyme activity was observed in 200 mM salt concentration at Zinnia marylandica 'Double Zahara Fire Improved'. MDA and H2O2 levels were observed higher in Zinnia elegans 'Zinnita Scarlet'.To conclude; it may be said that these two Zinnia varieties can tolerate salt concentration up to 150 mM.