Although most pregnant women with myoma are asymptomatic, myoma torsion or degeneration can cause pain and lead to emergent surgery. Unfortunately, pregnancy and myomas with degenerative changes make the diagnosis challenging. MRI can help to diagnose myoma as well as to guide proper treatment. A 24-year-old primigravida with abdominal pain was transferred to our hospital at 16+1 weeks of gestation age. Sonography showed probable right adnexal cystic mass. MRI was taken to differentiate ovarian cyst torsion and appendicitis. It revealed cystic degeneration of a myoma. Emergent laparoscopy was performed. Intraoperatively, the cystic-degenerative myoma was rotated counter-clockwise. Removal of myoma was carried out safely. Maternal and fetal condition were stable. Afterward, the patient was followed up on routine schedule without any problems. Through this case, MRI could be useful to determine accurate diagnosis of cystic change myoma and make decision to surgical intervention.