Transcription factors (TFs) and microRNAs (miRNAs) are tightly linked to each other in tumor development and progression, but their interactions in gastric cancer (GC) metastasis remain elusive. Here we report a novel suppressive role of GATA6 in inhibiting GC metastasis by transactivating miR-520b. We found that GATA6 expression was significantly downregulated in metastatic GC cells and tissues and that its downregulation was correlated with a poor GC prognosis. Overexpression of GATA6 suppressed GC cell migration, invasion and metastasis both in vitro and in vivo. Luciferase reporter assays and chromatin immunoprecipitation assays demonstrated that miR-520b is a direct transcriptional target of GATA6. Moreover, miR-520b expression was positively correlated with GATA6 expression in GC tissues, and ectopic expression of miR-520b inhibited the migration and invasion of GC cells. Furthermore, cAMP responsive element binding protein 1 (CREB1) was identified as a direct and functional target of miR-520b, and GATA6 could suppress GC cell migration and metastasis via miR-520b-mediated repression of CREB1. Downregulation of GATA6 and miR-520b may partly account for the overexpression of CREB1 in GC. In conclusion, our results provide novel insight into the TF-miRNA regulatory network involved in GC metastasis. Targeting the GATA6/miR-520b/CREB1 axis may be an effective approach for GC treatment.