Salinity is a major abiotic constraint affecting seed germination and plant growth. The effects of salt stress and salicylic acid (SA) and 2-aminoindan-2-phosphonic acid (SA synthesis inhibitor, AIP) on seed germination were investigated using kale (Brassica oleracea var. acephala) variety ‘Nagoya’. The results showed that the seed vigor of kale was significant decreased under 150 or 200 mmol·L ^-1 NaCl treatment by significantly reducing seed water uptake rate, seed vigor, and seedling quality, inhibited phenylalanine ammonia and lyase activity, decreasing endogenous SA content, and increasing hydrogen peroxide (H₂O₂) and superoxide anion (O₂ ^-.) contents. SA treatment effectively alleviated the inhibition of salt stress on seed germination, promoted endogenous SA anabolism, increased seed water absorption rate and seed vigor, promoted K ⁺ and Mg ²⁺ absorption, and reduced the Na ⁺ content. Furthermore, SA treatment significantly increased superoxide dismutase and peroxidase activities and inhibited H₂O₂ and O₂ ^-.accumulation. By contrast, AIP treatment significantly inhibited the germination process under salt stress, likely due to the reduced level of endogenous SA. This study demonstrates that exogenous SA enhances salt tolerance in kale seeds primarily through increasing the protective enzyme activities, reducing reactive oxygen species accumulation, and maintaining ion homeostasis during seed germination.