The presence of an appendix vermiformis in a femoral hernia sac is called De Garengeot's hernia. It is a very rare clinical condition and requires emergency surgery. However, preoperative diagnosis of De Garengeot's hernia is difficult. Herein, we report a 58-year-old female who presented with sudden-onset painful swelling in the right groin region. Diagnosis was established based on computed tomography findings, and appendectomy with mesh-free hernia repair was performed. The postoperative period was uneventful, and the histopathologic examination of the specimen revealed gangrenous appendicitis.