The NAC family is a multigene family that present uniquely in plants and whose members are involved in many important cellular processes including abiotic stress tolerance. In this study, sequences of two ATNAC3-related genes (SlNAC3) were identified in the tomato genome using different bioinformatics approaches. Phylogenetic analysis clustered 84 tomato identified NAC proteins into 19 different subfamilies that included 5 subfamilies for stress-related NAC genes with SlNAC3 members clustered with previously characterized ATNAC3 members from Arabidopsis. Gene expression analysis of SlNAC3 genes indicated that both of them are expressed in response to drought and salinity stress conditions. The over-expression of two stress-related SlNAC3 in tomato plants resulted in enhanced drought and salt tolerance when compared with wild type plants. The identified stressrelated NAC genes could be a useful tool to improve tomato productivity under stress conditions.