The WRKY family of transcription factors plays important roles in plant growth, defense regulation, and the stress response. However, in tomato (Lycopersicon esculentum), the WRKY mechanism of drought tolerance has not been described. In this study, we cloned the SlWRKY17 WRKY gene from tomato and induced its expression with PEG6000, NaCl, and abscisic acid (ABA). SlWRKY17 was located in the nucleus. The analysis of yeast transcriptional activity showed that SlWRKY17 may have transcriptional activation activity. Overexpressing SlWRKY17 in tobacco resulted in stronger drought tolerance. After the drought treatment, transgenic plants had higher superoxide dismutase, peroxidase, and catalase activities, as well as ascorbic acid (AsA) protein and relative water contents, but lower malondialdehyde content. In addition, several genes related to the ABA signaling pathway, proline biosynthesis, and the reactive oxygen species scavenging system were significantly upregulated in the transgenic lines. These results show that SlWRKY17 increases drought tolerance in tobacco. These results provide clues for the participation of SlWRKY17 in the regulation of abiotic stress tolerance. [ABSTRACT FROM AUTHOR]