<p>Gastrointestinal stromal tumour’s (GISTs) are the most common mesenchymal tumour of the gastrointestinal tract, with duodenal involvement being uncommon. Tumours arising from the duodenojejunal (DJ) flexure are particularly rare and pose diagnostic and surgical challenges due to their deep anatomical location and proximity to major vascular structures. We report a rare case of a large DJ flexure GIST in a 55-year-old male presenting with a progressively enlarging abdominal mass and early satiety. Contrast-enhanced computed tomography demonstrated a large exophytic tumour arising from the fourth part of the duodenum with extension into the proximal jejunum. The patient underwent exploratory laparotomy with en-bloc tumour resection and physiological reconstruction by infracolic duodenojejunal anastomosis. Histopathology confirmed a spindle cell type GIST with negative resection margins. This case highlights the importance of detailed preoperative imaging assessment and meticulous surgical planning in managing rare DJ flexure GISTs.</p>