Postmenopausal abnormal uterine bleeding is a common clinical problem addressed in gynaecological practice and should prompt clinical investigation due to the significant prevalence of malignant and premalignant lesions of the endometrium in this age group. Nevertheless, other causes should be considered, since its diagnostic and therapeutic management may differ considerably. Here, we present a case of a colouterine fistula due to chronic diverticulitis presenting with postmenopausal abnormal uterine bleeding. This is an infrequent occurrence and is caused by the rupture of a diverticular abscess into the uterine wall, resulting in an inflammatory adhesion of the colon and uterus, with necrosis and subsequent fistula formation. The clinical presentation is variable and may include abdominal pain, gastrointestinal tract symptoms, vaginal discharge, and abnormal uterine bleeding. The laboratory and imaging techniques may be not completely conclusive and definitive diagnosis can be made intraoperatively. There are different treatment options, with en bloc resection and primary anastomosis being used most often, allowing complete treatment. The prognosis for a colouterine fistula secondary to diverticulitis is excellent after surgery. This case highlights the importance of clinical suspicion of an unusual cause of uterine bleeding and an effective and multidisciplinary approach that allowed complete surgical treatment and patient recovery.