The aim of the current study was to investigate the effects of glycinebetaine (GB) on oxidative stress and some key growth parameters in maize (Zea mays L. 'DK 647 F1') grown under saline conditions. Maize seedlings were grown in pots containing perlite. The experiment was designed in a 2 x 2 factorial arrangement with 2 levels (0 and 100 mM) of sodium chloride (NaCl) and 2 levels (25 and 50 mM) of GB sprayed onto leaves of maize seedlings. Saline stress caused a considerable decline in total dry matter, chlorophyll content, relative water content (RWC), peroxidase (POD; EC. 188.8.131.52), and catalase (CAT; EC. 184.108.40.206); however, it increased proline, polyphenol oxidase (PPO; 220.127.116.11), and electrolyte leakage. Foliar application of both GB doses mitigated the deleterious effects of salinity stress to variable extents on the key growth parameters tested. As expected, sodium (Na+) concentrations were higher in the tissues of plants grown under saline conditions, and the GB treatments significantly reduced Na+ concentration in the plant tissues. Salinity stress reduced both calcium (Ca2+) and potassium (Kr+) in the leaves, and GB treatments increased concentrations of both elements in plant tissues; however, their levels were still lower than control values. In particular, foliar application of 50 mM GB mitigated some of the deleterious effects of salt stress by improving proline, Ca2+, and K+ levels and maintaining membrane permeability.