© 2014, International Institute of Anticancer Research. All rights reserved. Aim: We aimed to investigate the clinical significance of the activation of Yes-Associated Protein 1 (YAP1), a key downstream effector of Hippo tumor-suppressor pathway, in ovarian cancer. Materials and Methods: A gene expression signature reflecting activation of YAP1 was developed from gene expression data of 267 samples from patients with ovarian cancer. A refined ovarian cancer YAP1 signature was validated in an independent ovarian cancer cohort (n=185). Associations between the YAP1 signature and prognosis were assessed using Kaplan-Meier plots, the log-rank test, and a Cox proportional hazards model. Results: We identified a 612-gene expression signature reflecting YAP1 activation in ovarian cancer. In multivariate analysis, the signature was an independent predictor of overall survival (hazard ratio=1.66; 95% confidence interval=1.1 to 2.53; p=0.01). In subset analysis, the signature identified patients likely to benefit from taxane-based adjuvant chemotherapy. Conclusion: Activation of YAP1 is significantly associated with prognosis and the YAP1 signature can predict response to taxane-based adjuvant chemotherapy in patients with ovarian cancer.