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To investigate the role of tonoplast Na+/H+ antiporters (ZmNHX) in salt-stress resistance newly developed maize (Zea mays L.) SR hybrids and cv. Across 8023 were tested under low (50 mM NaCl) and high salinity (200 mM NaCl). Resistance to Na+ toxicity was monitored in terms of shoot growth and number of necrotic leaf spots. At high salinity, the SR hybrids showed better shoot growth than Across 8023. SR 03 and SR 05 had a lower number of necrotic spots per leaf compared to SR 20 and Across 8023. Based on these results, SR 03 and SR 05 were classified as salt-resistant, and SR 20 and Across 8023 as salt-sensitive genotypes. At 200 mM NaCl, the salt-resistant hybrids SR 03 and SR 05 showed a significant upregulation of the tonoplast Na+/H+ antiporter (ZmNHX) in leaves compared with Across 8023 and SR 20. The salt stress–induced increase in transcription of ZmNHX may lead to enhanced tonoplast Na+/H+ antiport in leaves for SR 03 and SR 05. Hence, sequestration of Na+ into leaf vacuoles contributes to salt resistance of these genotypes by protecting the cytoplasm from Na+ toxicity. Relative transcription of ZmNHX in roots was only increased in SR 20, which may explain the efficient Na+ exclusion from shoots of SR 20.