cAMP responsive element binding protein 1 (CREB1) gene, has been reported to play crucial roles in tumor progression and development in various types of cancer. Little is known, however, about its role and underlying mechanism in gastric cancer (GC). Herein, we investigated the biological roles and molecular mechanism of CREB1 in GC. The expression level was determined in four GC cell lines by quantitative RT-PCR and western blotting. Recombinant expression vector carrying small interfering RNA (siRNA) targeting CREB1 was constructed and then transfected into human GC cell line (SGC-7901). Cell proliferation, colony formation, cycle distribution, migration and invasion in vitro were determined by MTT, colony forming, flow cytometry, would healing and Transwell invasion assays after CREB1 knockdown. Tumor growth in vivo was assessed by measurement of tumor volume and weight in a nude mouse model. We found that CREB1 was highly expressed in the human GC cell lines. We also showed that knockdown of CREB1 in SGC-7901 cells significantly inhibited cell proliferation, colony formation, migration and invasion and induced cell arrest at G1/G0 phase in vitro, as well as suppressed tumor growth in vivo. In addition, CREB1 knockdown was able to significantly reduce expression of its downstream target genes cyclin D1, Bcl-2 and MMP-9 in vitro and in vivo. These findings suggest that CREB1 may be a potential therapeutic target for the treatment of gastric cancer.