BACKGROUND This study aimed to investigate the role of micro-RNA 205-5p (miR-205-5p) in the progression of gastric cancer, and the target of miR-205-5p in human gastric cancer cells in vitro. MATERIAL AND METHODS Expression of miR-205-5p and PTEN in gastric cancer tissue samples and adjacent normal gastric tissue from 35 patients was studied using immunohistochemistry and in situ hybridization. SGC-7901 human gastric cancer cells included a normal control (NC) group, a group transfected with empty vector (Vector), a group treated with miR-205-5p inhibitor (miR-inhibitor), and a group treated with miR-205-5p inhibitor and small interfering PTEN mRNA (miR-inhibitor+si-PTEN). Quantitative reverse transcription polymerase chain reaction (qRT-PCR) measured miR-205-5p expression, cell proliferation was measured by MTT assay, cell apoptosis by flow cytometry, transwell and wound healing assays measured cell migration, and transmission electron microscopy (TEM) showed ultrastructural changes in SGC-7901 cells. PTEN, AKT and p-AKT protein expression were measured using Western blot. The correlation between miR-205-5p and PTEN was analyzed using a dual-luciferase reporter assay. RESULTS Increased expression of miR-205-5p and PTEN in gastric cancer tissues were correlated with tumor stage. In SGC-7901 cells, miR-205-5p mRNA expression in the miR-inhibitor and miR-inhibitor+si-PTEN groups was significantly lower than that in the NC group (P<0.001). In the miR-inhibitor group, cell proliferation was significantly decreased, and apoptosis was significantly increased (P<0.001). CONCLUSIONS In gastric cancer, increased expression of miR-205-5p was associated with tumor stage, and in SGC-7901 cells PTEN was a target gene for miR-205-5p.