Background Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the alimentary tract. They are usually manifested by GI bleeding. Case Presentation A 53-year-old male patient was admitted to the hospital for elective inguinal hernia repair. The patient did not have any history of GI symptoms in the past. A day after open inguinal hernia repair, the patient developed recurrent attacks of hematemesis resulting in hemodynamic instability and admission to the intensive care unit. An upper GI endoscopy identified a small bleeding gastric lesion. After multiple failed attempts to control the bleeding endoscopically, an emergency exploratory laparotomy was performed. An unexpected large fungating bleeding gastric mass was detected. The mass measured approximately 40 × 30 cm, and multiple peritoneal deposits were also discovered. A wedge resection of the anterior gastric wall along with the mass was performed. Histopathology revealed a high-grade (G2) GIST. Discussion GISTs appear in variable sizes and may lead to a variety of complications including abdominal pain, GI obstruction, and bleeding. This case highlights the unexpected presentation and sudden bleeding of a large GIST in a totally asymptomatic patient undergoing elective hernia surgery. It also illustrates that GIST can be asymptomatic and grow to large sizes before developing clinical manifestations. Conclusion The case report highlights a common complication of GIST with unexpected timing, immediately after routine hernia surgery.