An ovarian cyst is the most common presentation in gynaecology. Most of the cysts are benign but few can be malignant too. A 44 yrs old female visited to the hospital with pain right side lower abdomen and features of sepsis. Imaging revealed right side hemorrhagic cyst with suspected torsion. She was prepared for surgery. Per-operatively a ruptured right-side ovarian mass around 8x7 cm was present which appeared necrotic and fragmented. Histopathological examination showed endometroid carcinoma of ovary. Patient received 3 cycles of neo adjuvant chemotherapy and then underwent debulking surgery followed by 3 cycles of post op chemotherapy. Epithelial ovarian cancers may grow rapidly. Rupture of the cystic tumor and features of sepsis due to infected tumor fragments are infrequent in case of ovarian cancer. We report a rare case of ruptured ovarian endometroid tumour with features of sepsis. Malignancy should be considered in the differential diagnosis in middle aged women with ovarian cyst.