Pelvic pain is a common symptom in women of reproductive age. Acute pelvic pain with rapid onset demands prompt diagnosis and treatment. We report the case of a patient with ovarian incarceration of acute onset. To our knowledge, this is the first report of ovarian incarceration into the pelvic peritoneal sac in a woman of reproductive age. In the present case, laparoscopy was useful in establishing the cause of pelvic pain. The patient reported severe lower right quadrant abdominal pain of sudden onset. At laparoscopic examination, the right fallopian tube was normal; however, the right ovary was not initially visible at the normal site. After the swollen right ovarian ligament was pulled aside using nontraumatic laparoscopic forceps, we were able to detect incarceration of the right ovary into the peritoneal sac in the medial to right uterosacral ligament. This case is unique because of ovarian incarceration into the peritoneal fenestration. We believe this condition was congenital because there was no other cause such as previous surgery, severe endometriosis, or pelvic inflammatory diseases.