DREB transcription factors usually play important regulatory roles in the responses of plants to abiotic stress. In this study, a novel SlDREB1 transcription factor from tomato was isolated by yeast-one-hybrid system. Bioinformatics analysis showed that the SlDREB1 is a single copy gene with typical AP2 conserved domain, and located on the #6 chromosome of the tomato genome. The SlDREB1 protein was confirmed to be localized to the cell nucleus. To profile the physiological and molecular responses of the SlDREB1 gene to drought stress, we transferred the SlDREB1 gene into the Arabidopsis plants, and functionally characterized the SlDREB1 gene by molecular detection in vitro and drought stress experiments. The data showed that accumulation of the SlDREB1 mRNA in the roots of the tomato was higher than that in the shoots, and strongly induced by drought, salt or exogenous abscisic acid. Both transcriptional activation and gel mobility shift assay indicated that the SlDREB1 protein exhibited specific mechanism recognizing the CCGAC motif in the promoters of the stress-resistant genes in the transgenic Arabidopsis. The data exhibited that the transgenic Arabidopsis revealed obvious up-regulations in accumulations of the SlDREB1 and ERD15 mRNA in response to drought stress. Physiological measurements demonstrated that the transgenic Arabidopsis overexpressing the SlDREB1 gene remarkably increased accumulation of osmolytes, such as soluble sugar and free proline, but reduced the contents of malondialdehyde in the leaves, suggesting that overexpression of the SlDREB1 gene in the transgenic Arabidopsis plays crucial regulatory roles in maintaining the balance of osmotic potentials and alleviating physiological damage in response to drought stress. Northern blotting also provided evidence that the tomato SlDREB1 apparently up-regulated the expressions of the drought-resistant ERD15 gene through a transcriptional activation pathway recognizing the CCGAC motifs, such as the NNCCGACNN element in the promoter of the ERD15 instead of limiting to the specific DRE element in the promoter of the RD29A, and led to an enhanced tolerance of the transgenic Arabidopsis to drought stress.