Mesenteric lymphangioma is a benign cystic tumour of the lymphatic vessels that occurs rarely in adults. Due to the infrequency of cases and the insidious presentation, these tumours can be diagnosed late and become massive. Resection of mesenteric lymphangioma in its entirety is the recommended management in order to prevent recurrence. This case report describes the finding of a massive mesenteric lymphangioma (dimensions 420×470×100 mm) in a young man, the investigations leading to diagnosis, and the subsequent surgical management. The substantial size of this tumour produced considerable challenges for the surgical team, including involvement of adjacent small bowel and mesenteric vasculature. Preoperative diagnosis and assessment of the anatomy was pivotal in achieving a complete resection and a good patient outcome.