The germination response of seeds under artificial stress conditions is a tool for better understanding of the survival and adaptation ability of species under natural stress conditions. The aims of this study were to evaluate the protective effect of nitric oxide during germination as well as seed vigor and seedling development of Eucalyptus urophylla under salt stress conditions. The experimental design was completely randomized, with five replications, in a 3 × 3 + 1 factorial arrangement, with three priming factors [water, sodium nitroprusside (SNP), and potassium nitrate (KNO3)], three germination conditions (distilled water, and the water potentials of -0.6 and -1.2 MPa), and an additional control treatment (unprimed seeds). The following determinations were made: germination count at seven and fourteen days, germination speed index, primary root length, shoot length, and total length. SNP protects seeds, leading to a higher percentage of germination, as well as greater root growth and total seedling size, whereas KNO3 is not effective in protecting seeds that suffer from salt stress, which affects their physiological and morphological characteristics. E. urophylla seeds are sensitive to salt stress, and physiological priming with SNP leads to an increase in the percentage of germination, vigor, and seedling development under salinity conditions.