The case was a 66-year-old woman. During treatment for ulcerative colitis, she developed fever and was diagnosed with diverticulitis of the sigmoid colon and abscess formation by CT. She occasionally had symptoms such as fever and abdominal pain and had to undergo fasting treatment. On preoperative CT, diverticulitis of the sigmoid colon, abscess formation, and suspected left ovarian penetration were diagnosed. Intraoperative findings showed an abscess and fistula formation between the sigmoid colon and left ovary, so laparoscopy-assisted resection of the sigmoid and left ovary was performed. A rare case that developed diverticulitis of the sigmoid colon penetrating to the ovary is presented along with a review of the relevant literature.