We assessed the expression of Serpin Family E Member 1 (SERPINE1) and its prognostic values in gastric adenocarcinoma (GAC) by using the data from TCGA database. The biological functions of SERPINE1 in GAC cells were detected by cell counting Kit-8, colony-forming, Transwell, and wound-healing assays, appropriately. Relative mRNA and protein levels were detected by RT-qPCR and western blot. Bioinformatics analysis indicated that SERPINE1 was significantly up-regulated in GAC tissues compared to normal tissues. High SERPINE1 expression led to a short overall survival and could act as an independent prognosticator for GAC patients. Besides, down-regulation of SERPINE1 showed a suppressive effect on the phenotype of GAC cells and significantly inhibited the EMT process. Over-expression of SERPINE1 got the reverse outcomes. These data suggest that SERPINE1 contributes to the proliferation, invasion and migration of GAC cells, insinuating that SERPINE1 may be considered as a novel biomarker for GAC treatment.