<p>The application of amino acids has been shown to enhance plant growth and maintain physiological performance under salt stress. However, the role of methionine in salt tolerance in broccoli remains unexplored. In a pot experiment, foliar application of methionine (0, 10, 20, and 30 mg L^− 1) was applied to broccoli cultivars to assess its influence in salt stress conditions (0 mM, 60 mM, and 120 mM NaCl). Salt stress markedly impaired the yield, physiological and biochemical attributes of broccoli cultivars. Conversely, plants treated with methionine exhibited enhanced growth and yield traits in both cultivars under salt stress conditions. Additionally, methionine-treated plants increased the accumulation of secondary metabolites (phenolics, carotenoids, and ascorbic acid) and enhanced the accumulation of osmolytes (proline and glycine betaine) under salinity stress. It reduced oxidative stress by limiting the production of hydrogen peroxide and malondialdehyde under salt stress conditions. The Na⁺/K⁺ ratio in broccoli was maintained under salt stress conditions with methionine application. The activities of antioxidant enzymes- superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), and catalase (CAT) were also significantly enhanced in methionine-treated plants under salt stress conditions. The findings of the current study highlight the role of methionine at 30 mg L^− 1 in enhancing broccoli’s resistance to salt stress, filling a critical knowledge gap and suggesting a promising strategy to increase the yield of broccoli under conditions.</p>