Background: Primary ovarian fibrosarcomas are very rare tumours associated with an extremely poor prognosis. Most patients relapse or die within 2 years. Because of the low incidence, it is difficult to identify prognostic factors or to establish treatment guidelines. Case Report: In this report, we present a patient with the second relapse of an ovarian fibrosarcoma localised in the rectosigmoid. The tumour caused intussusception into the rectum, leading to large bowel obstruction. After complete resection of the tumour, the patient completely recovered. 28 months after primary diagnosis, follow-up did not show any signs of recurrent tumour disease. Conclusions: Reviewing the literature, it is recommended that all patients should primarily be operated on and generally be followed up closely. In patients with incomplete resection, palliative chemo- and/or radiotherapy is recommended. In our opinion, in patients with complete resection, adjuvant chemo- and/or radiotherapy should be considered. Only in patients with high-grade fibrosarcomas, adjuvant intra- or postoperative radiotherapy should be applied.