OBJECTIVE: Circular RNAs (circ-RNAs) have recently shown capabilities as gene regulators in mammals. In this study, we aimed to evaluate the effects and mechanism of circ_0009910 in gastric cancer (GC). PATIENTS AND METHODS: Circ_0009910 expression was quantified by Real-time PCR in human GC cell lines and tissues. Association between circ_0009910 levels and clinicopathological factors and patient's prognosis was analyzed. The roles of circ_0009910 in regulating GC cell proliferation, colony formation, migration, and invasion were evaluated in vitro. Western blot analysis was conducted to detect the expressions of molecular markers of epithelial-mesenchymal transition (EMT). RESULTS: Circ_0009910 expression level was elevated in GC tissues and cell lines and associated with clinical stage (p = 0.032), distant metastasis (p = 0.028) and differentiation (p = 0.007). Kaplan-Meier survival analysis indicated that circ_0009910 expression in positive group has a worse overall survival compared to the negative group (p = 0.0013). Multivariate analysis showed that circ_0009910 was an independent risk factor for GC (HR = 2.346, 95% CI: 1.673-3.775, p = 0.006). Knockdown of circ_0009910 expression can suppress BGC823 and AGS cells proliferation, migration and invasion in vitro experiments. The results of Western blot indicated that knockdown of circ_0009910 increased expression of E-cadherin and decreased expression of the mesenchymal markers, snail and N-cadherin. CONCLUSIONS: Altogether, we demonstrate that circ_0009910 acts as a prognostic biomarker and promote cell proliferation, migration, invasion and EMT in GC, indicating that circ_0009910 may be a novel potential biomarker and therapeutic target of GC.