Late embryogenesis abundant (LEA) genes encode highly hydrophilic proteins that are essential in abiotic stress responses. However, most LEA genes in higher plants have not yet been investigated. This study identified an LEA family gene (PtrLEA7) from Poncirus trifoliata and studied its function in drought tolerance. The full-length coding sequence of PtrLEA7 was 420 bp encoding a protein of 139 amino acids. Phylogenetic analysis shows that PtrLEA7 protein belongs to the LEA_4 subfamily. Expression profiling by qPCR found that PtrLEA7 was strongly induced by dehydration, cold and ABA treatments, and slightly induced by salt stress. Subcellular localization reveals that PtrLEA7 protein was located in both cytoplasm and nucleus. To investigate its function, transgenic plants of both tobacco and Poncirus trifoliata overexpressing PtrLEA7 were obtained. Stress tolerance assays show that overexpression lines had enhanced dehydration and drought tolerance compared with wild type plants, indicating that PtrLEA7 positively regulates drought tolerance. In addition, transgenic plants had much higher expression levels of three antioxidant enzyme genes (CAT, SOD and POD) and significantly increased catalase enzyme activity, accompanied by reduced reactive oxygen species accumulation in comparison with wild type plants. Collectively, this study demonstrates that PtrLEA7 can confer enhanced drought tolerance partially via enhancing antioxidant capacity.