CircRNAs have been shown to be associated with gastric cancer tumorigenesis. But little was known about the role of circPDZD8 in gastric cancer. CircPDZD8 was up-regulated in gastric cancer tissues and cells, Kaplan-Meier survival analysis indicated that gastric patients had a poor overall survival when circPDZD8 levels were high. CircPDZD8 knockdown could hinder proliferation and migration of gastric cancer cells. MiR-197-5p, which was down-regulated in gastric cancer, was shown to be a target of circPDZD8 and was inversely correlated with circPDZD8 expression. CHD9, as a target gene of miR-197-5p, was negatively regulated by miR-197-5p and positively correlated with circPDZD8 expression. Importantly, circPDZD8 could up-regulate CHD9 expression by sponging miR-197-5p, and modulate cell progression by regulation of the miR-197-5p/CHD9 axis in gastric cancer. CircPDZD8 knockdown repressed the progression of gastric cancer cells by sponging miR-197-5p and down-regulating CHD9.