The Hippo pathway regulates intrinsic organ sizes by regulating apoptosis and cell proliferation. YAP1 (yes-associated protein 1) is a transcriptional effector of the Hippo pathway. YAP1 expression is reported to be associated with gastric cancer carcinogenesis and malignancy. In this study, we compared the expression of YAP1 in gastric cancer and normal stomach tissues. Tissue microarray analysis was performed in 156 gastric cancer samples, 8 adjacent normal stomach tissues, and 4 normal stomach tissues. We also analyzed the association between YAP1 protein expression and clinicopathological features, such as age, gender, histological differentiation, and clinical stages. We used the ONCOMINE database and the Kaplan-Meier plotter to analyze YAP1 expression status in different clinicopathological parameters of gastric cancer. We also used the Kaplan-Meier plotter to summarize the survival information of YAP1 from a total of 631 gastric cancer patients. YAP1 expression was found to be elevated in gastric cancer tissues compared to normal stomach tissues. YAP1 messenger RNA was found to be upregulated in gastric intestinal-type adenocarcinoma and gastric mixed adenocarcinoma compared to gastric mucosa. YAP1 high expression was found to be correlated to worse overall survival for all gastric cancer patients followed for 20 years. These results indicate that YAP1 can be used to predict the prognosis of gastric cancer. And YAP1 maybe a potential drug target for gastric cancer patients.