Growing evidence indicates that miRNAs play critical roles in tumorigenesis and cancer progression. Here, we report that miR-215 is significantly up-regulated in gastric cancer tissues from either gastrectomy or gastroscopy. Receiver Operator Characteristic (ROC) curve analysis indicated that miR-215 may be a candidate biomarker for gastric cancer diagnosis. Inhibition of miR-215 significantly suppressed gastric cancer cell proliferation possibly via G1 arrest. Further analyses indicated that miR-215 was able to target retinoblastoma tumor-suppressor gene 1 (RB1) through its 3'-UTR in gastric cancer cells. These data suggest that frequently up-regulated miR-215 in gastric cancer may influence cell proliferation by targeting RB1.