A diverticulum is a relatively common finding that is generally discovered incidentally; it is most commonly observed in the colon, followed by the duodenum. However, duodenal diverticulum perforation (DDP) is a rare complication. Due to its rarity, its diagnosis is often challenging and the appropriate treatment remains unclear, possibly contributing to its high mortality rate. Traditionally, surgical repair is the primary mode of treatment. However, with the recent advancements in medical technology, conservative management such as bowel rest and endoscopic drainage help successfully manage DDP. Duodenal diverticulum bleeding (DDB) is a rare cause of upper gastrointestinal bleeding. While endoscopic, angiographical, and surgical treatments have been performed to achieve hemostasis, there is no consensus regarding the optimal treatment for DDB. We describe a case of a perforated duodenal diverticulum (DD) with postoperative diverticulum bleeding. Our patient, an elderly female, complained of abdominal pain. Computed tomography images revealed free air in the retroperitoneum, and gastrointestinal perforation was suspected. During the emergency surgery, a perforated DD was detected in the third portion of the duodenum. Due to severe inflammation, diverticulectomy was not performed as it was deemed risky. Instead, we directly sutured the orifice using an omental patch. Duodenal leakage was observed from postoperative day (POD) 3 with bleeding from the remnant DD occurred on PODs 6 and 13. An attempt at endoscopic hemostasis failed, but transcatheter arterial embolization (TAE) was successfully performed. The postoperative course was complicated, and the patient died on POD 54. To the best of our knowledge, this is the first report on DD perforation with postoperative DDB. The remnant DD may be damaged by the digestive juices and result in bleeding. Precautionary measures for duodenal leakage should be undertaken when the DD is unresectable. Additionally, TAE is effective for postoperative DDB.