Appendiceal mucocele is a rare mucin-producing neoplasm of appendiceal origin. Due to its location and imaging findings, appendiceal mucocele is easily confused with tumors of the right adnexa. We present a rare case of a patient initially misdiagnosed with an ovarian tumor intraoperatively diagnosed as an appendiceal mucocele and successfully treated. A 66-year-old postmenopausal woman was admitted to the gynecology department for an asymptomatic pelvic mass. Preoperative pelvic imaging showed an 8-cm cystic mass. Exploratory laparoscopy for the suspected epithelial borderline tumor from the right ovary revealed a cystic mass in the right pelvic area and normal uterus, fallopian tubes, and ovaries. Intraoperative consultation with the general surgery department confirmed the appendiceal origin. Laparoscopic appendectomy was performed. Histopathological examination confirmed a low-grade mucinous neoplasm of appendiceal origin. The patient was discharged on a postoperative day 5 without complications. The outpatient follow-up performed 1 month later showed no evidence of disease progression. Despite the use of advanced diagnostic tools, appendiceal mucocele may be confused for ovarian malignancies. Because the clinical features of appendiceal mucocele are nonspecific, clinicians and radiologists know the specific imaging findings. A multidisciplinary approach including general surgery, gynecology, and radiology is required for preoperative diagnosis and treatment.