Long non-coding RNAs (IncRNAs) act as tumor suppressors or oncogenes in tumor development and progression. In the present study, we explored the expression and biological role of the IncRNA DNM3OS in gastric cancer (GC). We observed that DNM3OS was upregulated in GC tissues and cell lines, and high DNM3OS expression was correlated with malignant features and served as an indicator of a poor prognosis for GC patients. DNM3OS knockdown inhibited the proliferation of GC cells, and reduced DNM3OS suppressed tumor growth in vivo. Moreover, DNM3OS depletion inhibited the migration and invasion of GC cells through the suppression of the Snail-mediated epithelial-mesenchymal transition (EMT). In conclusion, we demonstrated that DNM3OS serves as an oncogenic IncRNA in GC, and we implicated DNM3OS as a promising prognostic factor and a potential therapeutic target for GC patients. (C) 2019 Elsevier Inc. All rights reserved.