Abstract <p>Salinity is a major abiotic stress that severely limits vegetable crop productivity by disrupting plant growth, inducing oxidative damage, and impairing physiological stability. Salicylic acid (SA) is a key signaling molecule involved in plant stress tolerance; however, its role in improving salinity tolerance in cauliflower (<i>Brassica oleracea</i> L. var. botrytis L.) has not been fully clarified. This study evaluated the effects of foliar SA application on growth, physiological performance, and biochemical responses of cauliflower seedlings grown under different NaCl concentrations (0, 50, 100, and 150 mM). Three SA doses (0, 0.25, and 0.50 mM) were applied in a randomized block design. Increasing salinity significantly decreased seedling height, biomass accumulation, leaf number, and chlorophyll content, while markedly increasing thiobarbituric acid reactive substances (TBARS) and H₂O₂ accumulation. SA application, particularly at 0.25 mM, mitigated salinity-induced growth reduction, improved chlorophyll stability, and reduced oxidative damage by enhancing osmotic adjustment (proline) and protein accumulation. Principal component analysis demonstrated that more than 75% of the total variation was explained by the first two components, clearly distinguishing stress and recovery responses. Overall, SA effectively alleviated salt-induced oxidative stress and improved physiological stability in cauliflower seedlings, indicating its strong potential as a bioregulator to enhance salinity tolerance in Brassica crops.</p>