Coronatine (COR) is a chlorosis-inducing phytotoxin that mimics some biological activities of methyl jasmonate. This study investigated whether COR confers salinity tolerance to cotton and whether such tolerance is correlated with changes in the activity of antioxidant enzymes. COR at 0.01microM was applied hydroponically to cotton seedlings at the two-leaf stage for 24h. A salinity stress of 150mM NaCl was imposed after completion of COR treatment for 15d. Salinity stress reduced biomass of seedlings and increased leaf superoxide radicals, hydrogen peroxide, lipid peroxidation, and electrolyte leakage. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and glutathione reductase (GR), and of the stable free radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH), scavenging activity were altered by salinity to varying degrees. Pretreatment with COR increased the activities of CAT, POD, GR, and DPPH scavenging activity in leaf tissues of salinity-stressed seedlings. Thus, COR might reduce the production of reactive oxygen species by activating antioxidant enzymes and DPPH-radical scavenging, thereby preventing membrane peroxidation and denaturation of biomolecules.