Glutathione S-transferases (GSTs) play a crucial role in responding to abiotic stress and are an important target for research on plant stress tolerance mechanisms.Populus euphraticais a promising candidate species for investigating the abiotic tolerance mechanisms in woody plants. In our previous study,PeGSTU58was identified as being associated with seed salinity tolerance. In the present study,PeGSTU58was cloned fromP.euphraticaand functionally characterized.PeGSTU58encodes a Tau class GST and is located in both the cytoplasm and nucleus. TransgenicArabidopsisoverexpressingPeGSTU58displayed enhanced tolerance to salt and drought stress. Under salt and drought stress, the transgenic plants exhibited significantly higher activities of antioxidant enzymes, including SOD, POD, CAT, and GST, compared to the wild-type (WT) plants. Additionally, the expression levels of several stress-responsive genes, includingDREB2A,COR47,RD22,CYP8D11, andSOD1were upregulated inPeGSTU58overexpression lines compared to those in WTArabidopsisunder salt and drought stress conditions. Furthermore, yeast one-hybrid assays and luciferase analysis showed that PebHLH35 can directly bind to the promoter region ofPeGSTU58and activate its expression. These results indicated thatPeGSTU58was involved in salt and drought stress tolerances by maintaining ROS homeostasis, and its expression was positively regulated by PebHLH35.