The study was conducted in order to determine the effects of exogenous selenium (Se) supply (5, 10, or 20 μM) on the resistance of cucumber (Cucumis sativus L.) cv. Polan F1 seedlings to salt stress (50 mM NaCl). Plant growth was negatively affected by excessive salinity and dry mass production as well as photosynthetic pigments accumulation severely decreased. Se treatments at 5 and 10 μM significantly improved the growth rate and increased the photosynthetic pigments and proline contents in cucumber leaves subjected to salt stress. Moreover, it is concluded that Se enhanced the salt tolerance of seedlings by protecting the cell membrane against lipid peroxidation. The growth-promoting effect of low Se concentrations (5 and 10 μM) under saline conditions could be due to the antioxidative activity of Se, increase in proline accumulation and/or decrease in content of chloride ions in the shoots tissues. Thus, optimal Se supplementation presents a promising potential for use in conditions of relatively high levels of NaCl in the medium.