Nitric oxide (NO) is a bioactive and a multifunctional gaseous molecule signal playing a central role and mediating variety of physiological processes in plants. In this study, the protective effect against chilling stress of exogenously applied sodium nitroprusside (SNP, a NO donor) in Cucumis sativus L. cv ZND407 and cv ZND461 was investigated. The SNP was sprayed over cucumber seedlings using different doses at 4°C. The results indicated that malondehyde (MDA) content was decreased however, soluble sugar and chlorophyll content increased upon treatment with 1.0 mmoll