MicroRNAs (miRNAs) are a group of critical players in gastric cancer (GC). Among numerous cancer-related miRNAs, the expression level and functional role of miR-345 in GC has not been investigated. This study showed that miR-345 expression was decreased in GC. Decreased expression level of miR-345 was associated with occurrence of lymph metastasis and advanced TNM stage of GC patients. Patients with low expression level of miR-345 had reduced overall survival (OS) and disease-free survival (DFS). In vitro experiments showed that miR-345 could inhibit the migration and invasion of GC cells. In vivo experiments showed that miR-345 knockdown could promote lung metastasis of GC cells in nude mice. miR-345 was found to prevent the metastasis by inhibiting epithelial-mesenchymal transition (EMT) of GC cells. Furthermore, FOXQ1 was confirmed to be the downstream target of miR-345 in GC cells. Forced expression of FOXQ1 could reverse the inhibitory effects of miR-345 on GC metastasis, while knockdown of FOXQ1 prevented the promoting effects of miR-345 knockdown on GC metastasis. In summary, this study demonstrates miR-345 is a promising biomarker and therapeutic target in GC.