Although gastrointestinal stromal tumours (GISTs) mostly present as solid tumours, they may rarely manifest as cystic lesions. A 52-year-old man presented with a large globular lump in the supraumbilical region for 5 months. Triphasic CECT showed a large, lobulated, heterogeneously enhancing solid cystic mass suggestive of exophytic GIST arising from antropyloric angle. USG-guided FNAC revealed bland spindle cells consistent with GIST. Preoperative treatment with imatinib showed no response. Intraoperatively, there was approximately 20 × 15 × 10 cm lobulated cystic lesion seen attached to pyloroduodenal junction containing brownish-coloured serous fluid. Histopathology report came as duodenal GIST with DOG-1, CD-117, CD-34, desmin, and SMA positivity. Follow-up of 1.5 years revealed no evidence of recurrence. GISTs should be considered as one of the possibilities while dealing with any cystic lesions in the gastrointestinal tract. Prompt surgical intervention in view of non-responsiveness to neoadjuvant chemotherapy was pivotal for proper management of our patient.