In this study, the efficacy of hyperthermia as an adjuvant treatment was assessed for patients with advanced epithelial ovarian cancer complicated by ascites. Forty-eight patients with advanced ovarian cancer and ascites were randomly assigned to two groups. Group A was treated with both hyperthermia (BSD-2000 Hyperthermia System) and chemotherapy (the GT regimen). Group B was treated only with the GT regimen. The curative effects, side effects, Karnofsky Performance Score (KPS), and immune indexes were assessed after two cycles of treatment for both groups. The response rate of Group A was significantly higher than that of Group B (50.0% vs. 25.0%, P<0.05). The median progression-free survival time for Group A was 8.2 months, as compared to 4.8 months for Group B (P<0.05). There was no significant difference between the groups in the disease control rate, overall survival, or improvement in the KPS score. Compared with Group B, the number of CD3+, CD4+, and CD8+ cells in Group A increased remarkably, while the CD4+/CD8+ ratio declined after the treatment (P<0.05 for all). These results suggest that hyperthermia is a promising adjuvant therapy for late-stage ovarian cancer. A future large-scale randomized clinical trial is warranted to confirm this conclusion.