Dianthus barbatus is an important and widely cultivated ornamental species in temperate regions, valued for its aesthetic appeal and use as both bedding and cut flowers, holding a significant position in the floriculture market. Salinity is a major environmental stress that adversely affects plant growth and performance. This study investigated the effects of 1 mM salicylic acid (SA) on the growth, biochemical, and physiological characteristics of D. barbatus under salt stress. SA application under non-stress conditions significantly increased leaf number, leaf area, and shoot fresh and dry weight. Under salinity levels of 3, 6, and 9 dS•m⁻¹, SA partially alleviated reductions in leaf area and fresh weight, although no significant improvement was observed at the highest salinity level. Additionally, SA enhanced phenolic and flavonoid content, increased antioxidant enzyme activities (SOD and CAT), improved total antioxidant capacity, and reduced electrolyte leakage at all salinity levels, with the greatest effect at 6 dS•m⁻¹. SA also contributed to maintaining or increasing soluble protein, proline, and potassium levels while reducing sodium accumulation in leaves, indicating an ion exclusion mechanism employed by D. barbatus to cope with salt stress. Application of SA, a natural hormone effective at low concentrations, may serve as a cost-effective strategy to enhance growth and salt tolerance in D. barbatus and other ornamental species, potentially reducing losses caused by salinity stress and increasing their economic value.