Gastric cancer (GC) is one of the most common malignancies of digestive system with aggressive phenotypes. Circular RNAs (circRNAs) play a pivotal function in cancer initiation and development. Nevertheless, the function and mechanism of circRNAs in gastric cancer (GC) is not fully understood. We found circ-ERBB2 was strikingly increased in GC tissues and cells. Noticeably, circ-ERBB2 upregulation in tumorous tissues was linked to patients' tumor size, depth of invasion, and overall survival. A series of gain and loss-of-function assays indicated its oncogenic role in GC cells, including cell proliferation, apoptosis, migration and invasion. We further predicted and identified circ-ERBB2 sponged miR-503 and miR-637 by bioinformatics analysis and luciferase reporter system. CACUL1 and MMP-19 were then predicted and confirmed as the target of miR-503 and miR-637, respectively. Furthermore, rescue assays indicated that circ-ERBB2 promoted tumor growth and invasion via miR-503/CACUL1 and miR-637/MMP-19 pathways, respectively. In summary, these findings demonstrated that circ-ERBB2 functions as an oncogene in GC and might be useful in developing promising therapies for this fatal malignancy. (C) 2019 Elsevier Inc. All rights reserved.