Despite exhaustive efforts to detect early-stage ovarian cancers, greater than two-thirds of patients are diagnosed at an advanced stage. Although diaphragmatic metastasis is not rare in advanced ovarian cancer patients and often precludes optimal cytoreductive surgery, little is known about the mechanisms and predictive factors of metastasis to the diaphragm. Thus, as an initial step toward investigating such factors, the present study was conducted to characterize the pathological status of ovarian cancer patients who underwent debulking surgery in combination with diaphragmatic surgery. This is a retrospective and cross-sectional study of patients who underwent debulking surgery in combination with diaphragmatic surgery at our institution between January 2005 and July 2015. Clinicopathological data were reviewed by board-certified gynecologists, pathologists, and cytopathologists. The rates of various pathological findings were investigated and compared by Fisher exact test between 2 groups: 1 group that was pathologically positive for diaphragmatic metastasis (group A) and another group that was pathologically negative for diaphragmatic metastasis (group B). Forty-six patients were included: 41 patients pathologically positive and 5 pathologically negative for diaphragmatic metastasis. The rates of metastasis to the lymph node (95.8% vs 20%, P = 0.001) and metastasis to the peritoneum except for the diaphragm (97.6% vs 60.0%, P = 0.028) were significantly increased in group A compared with group B. However, no significant differences between the 2 groups were found for rates of histological subtypes (high-grade serous or non-high-grade serous), the presence of ascites, the presence of malignant ascites, exposure of cancer cells on the ovarian surface, blood vascular invasion in the primary lesion, and lymphovascular invasion in the primary lesion. Our study demonstrated that metastasis to the lymph node and nondiaphragmatic metastasis to the peritoneum are significantly associated with metastasis to the diaphragmatic peritoneum, indicating that these factors may be pathological predictors of diaphragmatic metastasis in patients with ovarian cancer. However, as the data available are not sufficient to demonstrate the predictive power of these factors, a further comprehensive, large-scale study should be performed.