A 45-year-old Malay lady who presented with intermittent abdominal pain and a left hypochondrial mass was found to have a 10 x 8 x 5 cm duodenal tumour without local invasion at laparotomy. En bloc resection of the tumour with adequate margin of clearance was done and histopathological diagnosis of low grade leiomyosarcoma was made. Fourteen months later, she returned with multiple metastases in the liver and needed palliative chemotherapy for pain relief. Duodenal leiomyosarcomata are very rare tumour. Their prognostic indicators include biological grading, tumour size and presence of metastases. Recognition of its high malignant potential calls for close surveillance calls even after apparent curative surgery.