Gastric cancer (GC) is a malignant tumor with the highest incidence among all kinds of malignant tumors in China. Long noncoding RNAs (LncRNAs) have been reported to act as microRNA (miRNAs) sponges and thus play key roles in biological processes and pathogenesis. Thus, this study aimed to investigate the functional effects and the regulatory mechanism of lncRNA opa interacting protein 5-antisense 1 (OIP5-AS1) in gastric cancer cells. The expression of OIP5-AS1, miR-140-5p, Ubiquitin protein ligase E3 component n-recognin 5 (UBR5) was detected using quantitative real-time polymerase chain reaction (qRT-PCR). Cell proliferation, apoptosis, migration, and invasion were assessed using Cell-Counting Kit-8 (CCK-8), Flow cytometry, and Transwell assays. UBR5 protein level was detected by Western blot. Binding between miR-140-5p and OIP5-AS1 or UBR5 was predicted by Starbasev2.0 and TargetScan, and verified using Dual-luciferase reporter assays and RNA pull-down assay. A xenograft mice model was used to evaluate the effects of OIP5-AS1 on tumor growth in vivo. OIP5-AS1 was upregulated in GC cancer and cells. OIP5-AS1 knockdown inhibited cell proliferation, migration, invasion, but induced cell apoptosis in GC. In mechanism, OIP5-AS1 might serve as a sponge for miR-140-5p to enhance UBR5 expression. Moreover, overexpression of miR-140-5p or UBR5 partly reversed the effects of OIP5-AS1 depletion on the progression of GC cells. Furthermore, OIP5-AS1 depletion also suppressed tumor growth in vivo. OIP5-AS1 silencing might suppress proliferation, migration, invasion, and induced apoptosis in GC cells by regulating the miR-140-5p/UBR5 axis.