Long non-coding RNAs (lncRNAs) have emerged recently as important factors in regulating fundamental biological processes. Alterations in the expression and function of lncRNAs have been observed to promote tumor formation, progression and metastasis. Although downregulation of the expression levels of LET lncRNA in several tumors has been reported, its role in gastric cancer remains unknown. The aim of the present study was to investigate the expression and function of LET in gastric cancer development. The expression levels of LET in 37 pairs of gastric cancer and adjacent non-tumor tissues were detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). In addition, LET expression in gastric cancer cell lines was analyzed by RT-qPCR assay analysis. Furthermore, the impact of LET on cell proliferation, migration and apoptosis were detected using the cell counting kit-8, wound scratch and ELISA assays, respectively. The results demonstrated that the expression level of LET was downregulated in gastric cancer tissues and cell lines (SGC-7901 and MGC-803) compared with normal tissues and a normal human gastric epithelial cell line (GES-1). Restoration of LET expression using a synthesized recombinant overexpression vector transfected into SGC-7901 and MGC-803 cells, significantly inhibited cell proliferation and migration, and promoted cell apoptosis in vitro. The present study is the first to demonstrate that LET may function as a tumor suppressor in gastric cancer. The results indicate that LET may be a promising biomarker and/or a therapeutic target for gastric cancer.