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Introduction: Collision tumours are defined as two distant neoplasms co-existing in the same organ without histological intermixing. These tumours rarely occur in ovary. In preoperative imaging, these tumours are often missed and are diagnosed on histopathological examination. Here we report a case of ovarian collision tumours in a 35 years old female who presented with the complaints of abnormal uterine bleeding. Case summary: 35 year old parous women presented with complaints of frequent menstrual cycles. On examination her general condition was fair, abdominal examination revealed an abdominopelvic mass corresponding to 18weeks gravid uterus. Transabdominal and pelvic ultrasound findings indicated a broad bulky uterus and a multiloculated anechoic cystic lesion in the right adnexa, measuring 13.5 x 6.5 cm. CEMRI was suggestive of bilateral multiloculated ORADS IV lesions. Tumor markers were slightly elevated (CA125 68.6U/ml and CA 19.9 54.58U/ml). Patient underwent staging laparotomy. Histopathology report revealed a combination of serous borderline tumor and mature cystic teratoma left ovary and mucinous cystadenoma in right ovary. This case is notable for the coexistence of three distinct pathologies. Conclusion: The possibility of collision tumour should be considered when ovarian teratoma has imaging features unexplained by teratoma itself. Adequate excision and meticulous histopathological examination need to be done for understanding the various components of collision tumours to avoid them being misdiagnosed as malignancy.