A 55-year-old lady reported to the surgical OPD with clinical findings of acute peritonitis. Emergency laparotomy was performed. The peritoneal cavity was full of purulent material, however, the gut was normal. An 8 x 6 cm thick walled cyst was found in the left ovary with a minute perforation and purulent fluid coming out of it. Thorough peritoneal lavage along with left oophorectomy was performed. The postoperative recovery was smooth. Histopathology confirmed benign cystic teratoma of ovary.