Introduction: The ovarian tumours during pregnancy are uncommon. Torsion is the most common complication. Management can be conservative or surgical depending on the size, gestational age, available resources, and possibly patient preference following careful evaluation. Advances in imaging techniques have made decision making easier. Case report: We report a case of a 29 years old second gravida with 20 wks of pregnancy who presented to OPD with heaviness over lower abdomen. On abdominal examination a large abdominopelvic cystic mass was felt extending upto xiphisternum more on right side and 20wks uterus was felt deviated to left side. On radiological investigations she was diagnosed with a huge abdominopelvic cystic lesion of 22cm ×12cm× 22 cm with a live fetus of 20wks 6days. Patient was taken for laparotomy and proceed. Laprotomy revealed a huge right ovarian cyst filled with gelatinous material. Cyst excision along with ipsilateral salpingectomy was done . Histopathological report showed benign mucinous cystadenoma. Her pregnancy was followed up regularly and she delivered vaginally a healthy male baby at term. Conclusion: The management of ovarian tumours during pregnancy can be challenging. Although the safety of antepartum surgical intervention has been accepted, abdominal surgery will always carry some risk to a pregnant women and unborn fetus. Surgery becomes necessary in the presence of rupture, torsion or risk of malignancy.