Background: Cytoreductive surgery (CRS) in combination with hyperthermic intraperitoneal chemotherapy (HIPEC) is an option in advanced peritoneal sarcomatosis. Nevertheless, CRS and HIPEC are not successful in all patients. An enhancement of HIPEC using photodynamic therapy might be beneficial. Therefore, a combination of the photosensitizer Hypericin (HYP) with HIPEC was evaluated in an animal model. Procedure: An established HIPEC animal model for rhabdomyosarcoma (NOD/LtSz-scid IL2Rγnullmice, n=80) was used. All groups received HYP (100 µg/200 µl) intraperitoneally with and without cisplatin-based (30 or 60 mg/m2) HIPEC (37 or 42 °C, for 60 min) (five groups, each n=16). Tumor dissemination was documented visually and by using HYP-based fluorescence guidance. HYP-based photodynamic therapy (PDT) of the tumor was performed. Finally, tissue samples were evaluated regarding proliferation (Ki-67) and apoptosis (TUNEL). Results: HYP uptake even in smallest tumor nodes (< 1 mm) was found. HYP-based fluorescence guidance allowed a better tumor detection in comparison to visual inspection. Immunohistochemistry revealed HYP penetration across the tumor surface. HYP-based PDT without HIPEC induced marginal apoptotic effects at the tumor surface. Combining HYP with HIPEC revealed cisplatin concentration dependent decrease in proliferation capacity and induction of apoptosis across determined cell layers of the tumor surfaces. Conclusion: HYP as fluorescent photosensitizer offers an intraoperative diagnostic advantage detecting intraperitoneal tumor dissemination. The combination of HYP and cisplatin-based HIPEC was feasible in vivo showing enhanced effects on tumor proliferation and apoptosis induction across the tumor surface. Further studies combining HYP and HIPEC will follow to establish a clinical application.