Ovarian torsion (OT) during pregnancy is a rare condition that can cause maternal and fetal morbidity. Although the etiology of the disease is not fully understood, predisposing factors include increased ovarian size, free mobility, and long pedicle. The incidence of the disease increases after ovarian stimulation for the treatment of fertility. Diagnostic imaging modalities include ultrasonography and magnetic resonance imaging (MRI). A 28-year-old woman with a 33-week pregnancy presented to our emergency department with acute, severe left groin pain. According to the patient's declaration, she had her first pregnancy, which was acquired by intrauterine insemination in another center. Her vital signs were unremarkable except for tachycardia. Physical examination revealed guarding (défense musculaire) and rebound tenderness on the left lower quadrant of the abdomen. Laboratory and imaging studies were performed for the preliminary diagnosis of acute abdomen. She was diagnosed with OT and admitted to the department of obstetrics and gynecology. OT should be included in the differential diagnosis of patients with suspected acute abdomen in advanced stages of pregnancy. In addition, MRI should be used as an alternative diagnostic modality in patients with normal sonographic findings.