Human interacting protein X1 (PinX1) has been identified as a critical telomerase inhibitor and proposed to be a putative tumor suppressor gene. Loss of PinX1 has been found in a large variety of malignancies, but the expression status in epithelial ovarian tumors has not been investigated. In this study, immunohistochemistry for PinX1 protein was performed on a tissue microarray (TMA) of epithelial ovarian tumors (informatively containing 25 cystadenomas, 29 borderline tumors, and 157 invasive carcinomas) and 12 normal ovaries. Receiver-operator curve (ROC) analysis was used to determine cut-off scores for tumor positivity and to evaluate patients' survival status. The threshold for PinX1 positivity was determined to be above 60% (area under the curve = 0.856, P < 0.001) based on the area under the ROC. Positive expression of PinX1 was observed in 100% of normal ovarian tissues, in 84% of cystadenomas, in 75.9% borderline tumors, and 66.2% of ovarian carcinomas. Decreased expression of PinX1 was strongly related to patients with poor prognostic factors regarding presence of lymph node metastasis (P = 0.024), distant metastasis (P < 0.001), and late International Federation of Gynecology and Obstetrics (FIGO) stage (P < 0.001). In univariate survival analysis, a highly significant correlation between loss of PinX1 and shortened patient survival (mean, 48.2 months vs 99.2 months, P < 0.001) was displayed. Multivariate analysis demonstrated PinX1 expression (P = 0.027) was evaluated as an independent parameter. Our findings suggest that loss of PinX1 is an adverse independent molecular marker for epithelial ovarian carcinoma patients. PinX1 may be a novel target for telomerase-based anticancer therapy due to inhibiting telomerase activity.