With limited treatment options, intraperitoneal spread of ovarian cancer is a common problem leading to high morbidity. Intraperitoneal photodynamic therapy combined with debulking surgery to treat residual disease is an alternative choice for clinicians. Hematoporphyrin monomethyl ether (HMME) is a promising second-generation photosensitizer developed in China. Our study was designed to investigate the phototoxicity of HMME on ovarian cancer. NuTu-19, a cell line derived from adenocarcinoma of Fischer 344 rat, and its allogeneic graft ascites tumor model was used in this study. HMME was confirmed to be localized in cytolysosome, and HMME-based photosensitization induced direct necrosis as well as mitochondria damage. The photocytotoxicity of HMME was both light- and drug dose-dependent and no significant dark cytotoxicity was observed in NuTu-19 cells. With the ascite tumor-bearing Fischer 344 rat model, HMME-based intraperitoneal photodynamic therapy was proved to be useful in improving the prognosis of ovarian cancer. Thus, this study provides evidence that HMME-based photodynamic therapy is an effective adjuvant therapy for ovarian cancer.